Car Air Conditioning

Mercedes Benz Air Conditioning Compressor

2011-05-20T11:30:00.000-07:00

Let's remember that most of the A/C compressors that Mercedes Benz have used do not carry their own onboard oil supply. The refrigerant oil is delivered throughout the system via the refrigerant.
Just as you would not run your engine without oil people attempt to run the air conditioning compressors without oil. How does this happen? Underneath the hood of your car is a pretty hostile environment subject to all kind of heat, cold, and vibration. Over time refrigerant may be lost through the various seals and out the front of the compressor. Since the refrigerant carries the oil it stands to reason that when you lose refrigerant you lose the oil at the same time. If you fail to replace the oil when you add new refrigerant you might as well log on and start pricing a new compressor. If you are not doing the job yourself, do not assume that refrigerant oil has been added. You must ask and make sure. It will be cold when you pick it up but not for long.

Preventive maintenance goes a long way. When you open the hood do a visual inspection of your Mercedes air conditioning system. Check your air conditioning hoses, Mercedes compressor, and Mercedes condenser for signs of leaks, that is oil residue at any of the joints or on the parts. Failure to repair the problem may damage or destroy the compressor since you are losing the oil that lubricates the moving parts of the air conditioning system.

If your Mercedes air conditioner is not working properly do not use it until you can check it out. This may prevent further damage. Remember that your compressor turns on when you turn on the defroster too so do not assume that it can wait till spring to have it repaired.


Ok, now you realize your Mercedes A/C compressor is kaput so let's fix it right the first time. No use crying over spilled milk. The key now is to get you cool again and make sure you do not have any more problems.

Do not just bolt up another compressor without trying to analyze why this one went bad. Check for signs of leaks and make sure the auxiliary fan works. If the compressor clutch is white or shows signs of being subjected to extreme heat you can figure the compressor was intermittently locking up. This is due to lack of lubrication or internal breakage or both. Whatever the reason, shrapnel from the compressor was introduced into the system. Failures to remove this shrapnel will grenade your new Mercedes compressor. This is not covered under the warranty.

You must change the receiver drier when changing your new compressor. Just consider the receiver drier the oil filter for your air conditioning system. Some of that metal will be found there. By the way, if you do not change the drier the manufacturer will not warranty the compressor.

Another item that we recommend changing at this time is the expansion valve. These for the most part are easy to change and very inexpensive. The expansion valve allows the refrigerant to be sprayed on the evaporator. The orifices are very small and easily clogged by debris. You are not going to clean the valve so just change it now so you can assure yourself that when you install the new components described above the system will blow really cold air. It is a shame to redo the whole recharge over a part that costs approx $25.00 for many applications.

One last thought. If you are going to use a refrigerant other than what came in your vehicle check to make sure the refrigerant temperature switch you have installed on your drier is the right one for the refrigerant you are using. R134a uses a different switch than R12. The switch with the pigtail is the refrigerant temperature switch. These are temperature switches not pressure switches. Different refrigerants operate at different temperatures so double check your application.

Ps: It has been our experience that when the clutch is bad on your Mercedes compressor, it failed because of the scenario above. Don't waste your money just replacing the clutch. Change the compressor. We can argue that point till the cows come home but that is our opinion and we are sticking to it. We have seen to many people try it and lose. Why take a chance, besides when you see the price of a clutch versus the price of a compressor with a new clutch it becomes a no brainier.

System Inspection

2007-12-01T13:24:00.000-08:00

System Inspection

Although the A/C system should not be serviced by the do-it-yourselfer, preventive maintenance can be practiced and A/C system inspections can be performed to help maintain the efficiency of the vehicle's A/C system. For A/C system inspection, perform the following: The easiest and often most important check for the air conditioning system consists of a visual inspection of the system components. Visually inspect the air conditioning system for refrigerant leaks, damaged compressor clutch, abnormal compressor drive belt tension and/or condition, plugged evaporator drain tube, blocked condenser fins, disconnected or broken wires, blown fuses, corroded connections and poor insulation.
CHECKING FOR OIL LEAKS Refrigerant leaks show up as oily areas on the various components because the compressor oil is transported around the entire system along with the refrigerant. Look for oily spots on all the hoses and lines, and especially on the hose and tubing connections. If there are oily deposits, the system may have a leak, and you should have it checked by a certified air conditioning specialist.

KEEPING THE CONDENSER CLEAR Periodically inspect the front of the condenser for bent fins or foreign material (dirt, bugs, leaves, etc.). If any cooling fins are bent, straighten them carefully. You can remove any debris with a stiff bristle brush.

Without Sight Glass On vehicles that are not equipped with sight glasses, it is necessary to feel the temperature difference in the inlet and outlet lines at the receiver/drier to gauge the refrigerant level. Use the following procedure:

Locate the receiver/drier. It will generally be up front near the condenser. It is shaped like a small fire extinguisher and will always have two lines connected to it. One line goes to the expansion valve and the other goes to the condenser.
With the engine and the air conditioner running, hold a line in each hand and gauge their relative temperatures. If they are the same approximate temperatures, the system is correctly charged.
If the line from the expansion valve to the receiver/drier is a lot colder than the line from the receiver/drier to the condenser, then the system is overcharged. It should be noted that this is an extremely rare condition.
If the line that leads from the receiver/drier to the condenser is a lot colder than the other line, the system is undercharged.
If the system is undercharged or overcharged, have it checked by a professional air conditioning mechanic.

CHECKING THE REFRIGERANT LEVEL There are two ways to check refrigerant level. On vehicles equipped with sight glasses, checking the refrigerant level is a simple matter. Many late model vehicles, however, do not have a sight glass, and you have to check the temperature of the lines to determine the refrigerant level.

With Sight Glass The sight glass is normally located in the head of the receiver/drier. The receiver/drier is not hard to locate. It's a large metal cylinder that looks something like a fire extinguisher. Sometimes the sight glass is located in one of the metal lines leading from the top of the receiver/drier. Once you've found it, wipe it clean and proceed as follows:

With the engine and the air conditioning system running, look for the flow of refrigerant through the sight glass. If the air conditioner is working properly, you'll be able to see a continuous flow of clear refrigerant through the sight glass, with perhaps an occasional bubble at very high temperatures.
Cycle the air conditioner on and off to make sure what you are seeing is clear refrigerant. Since the refrigerant is clear, it is possible to mistake a completely discharged system for one that is fully charged. Turn the system off and watch the sight glass. If there is refrigerant in the system, you'll see bubbles during the off cycle. If you observe no bubbles when the system is running, and the airflow from the unit in the vehicle is delivering cold air, everything is OK.
If you observe bubbles in the sight glass while the system is operating, the system is low on refrigerant. Have it checked by a professional.
Oil streaks in the sight glass are an indication of trouble. Most of the time, if you see oil in the sight glass, it will appear as a series of streaks, although occasionally it may be a solid stream of oil. In either case, it means that part of the charge has been lost.

Governmental Regulations

2007-11-28T12:03:00.000-08:00

THE CLEAN AIR ACT 1990-SECTION 609

Our Threatened Ozone Layer

The ozone layer acts as a blanket in the stratosphere that protects us from harmful Ultra Violet (UV) radiation. Scientists worldwide believe that man-made chemicals such as CFC-12 (also known by the trade name Freon) are rapidly destroying this layer of gas 10-30 miles (16-48 km) above the earth's surface. Strong UV radiation breaks the CFC-12 molecules apart, releasing chlorine. A single chlorine atom can destroy over one hundred thousand ozone molecules. Ozone loss in the atmosphere is likely to lead to an increase in cataracts and skin cancer, which is now one of the fastest growing forms of cancer, and could weaken the human immune system. In the U.S., one person dies of skin cancer every hour. Agriculture, as well as plant and animal life, may also be dramatically affected.

Remember that ozone is "good up high, bad nearby": even though it protects us when it is in the stratosphere, ozone at ground level can be harmful to breathe and is a prime ingredient in smog. Many man-made sources such as tailpipe emissions from vehicles contribute to ground-level ozone.

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Global Action to Protect the Ozone Layer

The United States has joined over 160 countries as a party to the international treaty known as the Montreal Protocol. All developed countries agreed to phase out production of most ozone-depleting substances, including CFC's, by the end of 1995. The 1990 Clean Air Act Amendments (the Act) incorporated this production ban date and directed the EPA to develop regulations to maximize recycling, ban nonessential uses, develop labeling requirements and examine safe alternatives for ozone-depleting substances.

Impact of Motor Vehicle Air Conditioners

One of the largest uses of CFC-12 in the U.S. is as a refrigerant in Motor Vehicle Air Conditioners (MVACs). Section 609 of the Act gives the EPA the authority to establish requirements to prevent the release of refrigerants during the servicing of MVACs and to require recycling of refrigerants. Widespread refrigerant recycling reduces the demand for virgin CFC-12 and thus extends the time that it will be available. The following sections describe the requirements of the law and its potential impact on the service industry.

Handling CFC-12

VENTING

Another section of the Clean Air Act, section 608, prohibits releasing CFC-12 into the atmosphere. The prohibition on venting CFC-12 has been in effect since 1992.

SECTION 609 REGULATORY HISTORY

The original regulation promulgated under section 609 was published in July 1992. That regulation established standards for equipment that recovers and recycles CFC-12 refrigerant from motor vehicle air conditioners, rules for training and testing technicians to handle this equipment, and record-keeping requirements for service facilities and for refrigerant retailers. A supplemental final rule published in May 1995 established a standard for equipment that recovers but does not recycle CFC-12, as well as training and testing technicians to handle this equipment.

APPROVED EQUIPMENT

Technicians repairing or servicing CFC-12 MVACs must use either recover/recycle or recover-only equipment approved by the EPA. Recover/recycle equipment cleans the refrigerant so that oil, air and moisture contaminants reach acceptably low levels. A list of approved recover/recycle and recover-only equipment is available from the EPA.

TECHNICIAN TRAINING AND CERTIFICATION

Technicians who repair or service CFC-12 motor vehicle air conditioners must be trained and certified by an EPA-approved organization. Training programs must include information on the proper use of equipment, the regulatory requirements, the importance of refrigerant recovery, and the effects of ozone depletion. To be certified, technicians must pass a test demonstrating their knowledge in these areas. A list of approved testing programs is available from the EPA.

RECORDKEEPING REQUIREMENTS

Service shops must certify to the EPA that they own approved CFC-12 equipment. If refrigerant is recovered and sent to a reclamation facility, the name and address of that facility must be kept on file.

SALES RESTRICTIONS

Section 609 has long prohibited the sale of small cans of ozone-depleting refrigerants to anyone other than a certified technician. The sale of any size container of CFC-12 to anyone other than certified technicians was prohibited under section 608 of the Act beginning on November 14, 1994. This provision is intended to discourage "do-it-yourselfers" who recharge their own air conditioners. Such individuals often release refrigerant because they typically do not have access to recovery/recycling equipment. The EPA encourages "do-it-yourselfers" to bring their vehicles to certified technicians who can properly fix air conditioners using approved equipment. This avoids damage to A/C equipment by improper charging and helps to protect the environment.

Fig. 2: Common recovery machine used on R-134a systems

Handling HFC-134a Refrigerant

VENTING

Section 608 of the Clean Air Act prohibits releasing HFC-134a into the atmosphere. The prohibition on venting HFC-134a has been in effect since November 1995.

SECTION 609 REGULATORY HISTORY

In March 1996, the EPA proposed a rule to require recycling of HFC-134a. The rule proposed standards for recover-only and recover/recycle equipment and rules for training and testing technicians to handle this equipment.

APPROVED EQUIPMENT

Because of the venting prohibition described above, technicians who repair or service HFC-134a MVACs must recover the refrigerant. Any equipment may be used to recover the refrigerant, since equipment standards will not be in place until the effective date of the final rule. Technicians are not required to recycle HFC-134a refrigerant until the effective date of the final rule. At that time, technicians handling HFC-134a will have to either recycle the used HFC-134a refrigerant on-site, or send it to an off-site reclamation facility to be purified to ARI Standard 700, before it can be used to recharge A/C equipment.

After the effective date of the rule, the EPA will make available a list of approved recover/recycle and recover-only HFC-134a equipment.

CONVERTING CFC-12 EQUIPMENT FOR USE WITH HFC-134A

EPA regulations prohibit technicians from changing fittings on the same unit back and forth so that the unit is used for CFC-12 in the morning, HFC-134a in the afternoon, then back to CFC-12 again, etc.

EPA regulations specify that when equipment is converted for use with a new refrigerant, the converted unit must be able to meet the applicable equipment standard set forth in the regulations. CFC-12 equipment may be permanently converted for use with HFC-134a under certain conditions. The EPA intends to issue regulations placing certain restrictions on these retrofits in the future. Those restrictions may require that the manufacturer's service representative rather than the automotive service technician perform the retrofit, that a unit may only be retrofitted if retrofit procedures have been certified by an independent testing laboratory such as Underwriters Laboratories, and that an appropriate label is affixed to the unit. In addition, the retrofitted unit must meet the technical specifications of SAE standard J2210 and must have the capacity to purify used refrigerant to SAE standard J2099 for safe and direct return to the air conditioner following repairs.

In the absence of any EPA regulations, a service facility may perform such a retrofit, or may have the equipment manufacturer's service representative perform the retrofit, as long as the fittings are changed in accordance with the EPA's Significant New Alternative Policy (SNAP) program regulations. The Agency cautions technicians, however, that although recovering a given refrigerant using permanently converted equipment is legal, it may not be technically desirable. The equipment is designed to be compatible with specific refrigerants, and incompatible materials may cause short circuits, damage to seals, and compressor failure. Technicians should check with the recovery equipment manufacturer for recommendations about the recovery of refrigerants other than the refrigerant the equipment was originally intended to recover. Conversion of recovery equipment for use with other refrigerants may also invalidate any warranties offered by the equipment manufacturer.

TECHNICIAN TRAINING AND CERTIFICATION

Before the final rule is published and goes into effect, technicians repairing or servicing HFC-134a MVACs do not need to be trained and certified to handle HFC-134a. After the effective date of the rule, however, technicians who repair or service HFC-134a MVACs must be trained and certified by an EPA-approved organization. If a technician is already trained and certified to handle CFC-12, he will not need to be re certified to handle HFC-134a.

RECORDKEEPING REQUIREMENTS

Service shops must certify to the EPA that they own approved HFC-134a equipment.

NOTE: This certification is a one-time requirement, so that if a shop purchased a piece of CFC-12 recycling equipment in the past, and sent the certification to the EPA, the shop does not need to send a second certification to the EPA when it purchases a second piece of equipment, no matter what refrigerant that equipment is designed to handle. If refrigerant is recovered and sent to a reclamation facility, the shop must retain the name and address of that reclaimer.

SALES RESTRICTIONS

At the time of publishing, there is no restriction on the sale of HFC-134a, so anyone may purchase it. The EPA will issue a proposed rule under section 608 of the Act that will include a proposal to restrict the sale of HFC-134a so that only technicians certified under sections 608 and 609 may purchase it. After the proposed rule is published, the EPA will review comments from the public on the proposal and will then publish a final rule sometime in late 1998.

Handling Other Refrigerants that Substitute for CFC-12

VENTING SUBSTITUTE REFRIGERANTS

Other than HFC-134a, all EPA-accepted refrigerants that substitute for CFC-12 in motor vehicles, and that are currently on the market, are blends that contain ozone-depleting HCFC's such as R-22, R-142b and R-124. Section 608 of the Clean Air Act prohibits venting any of these new blend substitutes into the atmosphere. The prohibition on venting these ozone-depleting blends has been in effect since 1992.

SECTION 609 REGULATORY HISTORY

When the March 1996 proposed rule that requires recycling of HFC-134a was published in final form in the summer of 1997, it also established a standard for equipment that is designed to recover, but not recycle, any single, specific blend substitute refrigerant.

RECOVER ONLY EQUIPMENT

Technicians recovering these blend refrigerants must use EPA-approved equipment. As noted above, the final rule contains a standard for equipment designed to recover, but not recycle, a single, specific blend refrigerant. It may be possible to convert a piece of CFC-12 recover-only equipment so that it meets this standard-see the discussion on equipment conversions that follows this topic.

The EPA is currently working with independent testing laboratories and with equipment manufacturers to devise equipment that can recover, but not recycle, not only multiple blend refrigerants, but also contaminated CFC-12 and HFC-134a. Within the next year, the EPA will propose a standard for this type of equipment. The EPA expects that this equipment should be available by the 1998 A/C season.

CONVERTING CFC-12 RECOVER-ONLY EQUIPMENT FOR USE WITH BLEND SUBSTITUTES

The EPA regulations prohibit technicians from changing fittings on the same unit back and forth so that the unit is used for CFC-12 in the morning, a blend substitute in the afternoon, another blend substitute the next morning, HFC-134a the next afternoon, etc.

The EPA regulations specify that when equipment is converted for use with a refrigerant other than the refrigerant for which the equipment was originally intended, the converted unit must be able to meet the applicable equipment standard set forth in the regulations. CFC-12 recover-only equipment may be permanently converted for use with single, specific blend refrigerants under certain conditions. The EPA intends to issue regulations placing certain restrictions on these retrofits in the future. Those restrictions may require that the manufacturer's service representative rather than the automotive service technician perform the retrofit, that a unit may only be retrofitted if retrofit procedures have been certified by an independent testing laboratory such as Underwriters Laboratories, and that an appropriate label is affixed to the unit. In addition, the retrofitted unit has to meet the technical specifications of the EPA standard.

RECYCLING EQUIPMENT

The EPA regulations currently prohibit technicians from recycling blend substitute refrigerants, and the Agency is not aware of any equipment currently on the market designed to recycle any of these blends. After recovering the blend refrigerant from the MVAC system, it must, therefore, be sent off-site for reclamation.

The EPA is working with independent testing laboratories and with equipment manufacturers to determine whether recycling equipment can be developed to service these blends, without jeopardizing the health or safety of the technician and the integrity of the MVAC system. If it is possible to develop such equipment, the EPA will work with equipment and refrigerant manufacturers and with independent testing laboratories to develop an appropriate standard for the equipment.

CONVERTING CFC-12 RECOVER/RECYCLE EQUIPMENT FOR USE WITH BLEND SUBSTITUTES

At the time of publication, the EPA also currently prohibits the conversion of existing CFC-12 or HFC-134a recycling equipment for either temporary or permanent use with a blend refrigerant. In the future, the EPA may issue regulations allowing these conversions but placing certain restrictions on who performs the conversions, what models may be converted, etc.

TECHNICIAN TRAINING AND CERTIFICATION

Technicians who repair or service MVACs with these refrigerants must be trained and certified by an EPA-approved organization. If a technician is already trained and certified to handle CFC-12 or HFC-134a, he will not need to be re certified to handle the blend refrigerants.

RECORDKEEPING REQUIREMENTS

Service facilities that work on vehicles that use blend substitutes must certify to the EPA that they own approved equipment designed to service these refrigerants. Note that this certification is a one-time requirement, so that if a shop purchased a piece of CFC-12 or HFC-134a recycling equipment in the past, and sent the certification to the EPA, the shop does not need to send a second certification to the EPA when it purchases a second piece of equipment, no matter what refrigerant that equipment is designed to handle. If refrigerant is recovered and sent to a reclamation facility, the shop must retain the name and address of that reclaimer.

SALES RESTRICTIONS

Because these blends contain HCFC's, Section 608 regulations prohibit the sale of any size container of any of these blend refrigerants to anyone other than certified technicians. This prohibition began in November, 1994.

Retrofitting Vehicles to Alternative Refrigerants

Although section 609 of the Act does not govern retrofitting, section 612 of the Act, which describes the EPS's Significant New Alternatives Policy (SNAP) program, does require that when retrofitting a CFC-12 vehicle for use with another refrigerant, the technician must first extract the CFC-12, must cover the CFC-12 label with a label that indicates the new refrigerant in the system and other information, and must affix new fittings unique to that refrigerant.

In addition, if a technician is retrofitting a vehicle to a refrigerant that contains R-22, the technician must ensure that only barrier hoses are used in the A/C system. Finally, if the system includes a pressure relief device, the technician must install a high-pressure compressor shutoff switch to prevent the compressor from increasing pressure until the refrigerant is vented.

Refrigeration Cycle

2007-11-27T11:24:00.000-08:00

Any automotive air conditioning system employs four basic parts-a mechanical compressor, driven by the vehicle's engine; an expansion valve, which is a restriction the compressor pumps against; and two heat exchangers, the evaporator and the condenser. In addition, there is the refrigerant that flows through this system.

The belt-driven compressor uses engine power to compress and circulate the refrigerant gas throughout the system. The refrigerant passes through the condenser on its way from the compressor outlet to the expansion valve. The condenser is located outside the passenger compartment, usually in front of the vehicle's radiator. The refrigerant passes from the expansion valve to the evaporator, and after passing through the evaporator tubing, it is returned to the compressor through its inlet. The evaporator is located inside the vehicle's passenger compartment.

When the compressor starts running, it pulls refrigerant from the evaporator coil and forces it into the condenser coil, thus lowering the evaporator pressure and increasing the condenser pressure. When proper operating pressures have been established, the expansion valve will open and allow refrigerant to return to the evaporator as fast as the compressor is removing it. Under these conditions, the pressure at each point in the system will reach a constant level, but the condenser pressure will be much higher than the evaporator pressure.

The pressure in the evaporator is low enough for the boiling point of the refrigerant to be well below the temperature of the vehicle's interior. Therefore, the liquid will boil, remove heat from the interior, and pass from the evaporator as a gas. The heating effect produced as the refrigerant passes through the compressor keeps the gas from liquefying and causes it to be discharged from the compressor at very high temperatures. This hot gas passes into the condenser. The pressure on this side of the system is high enough so that the boiling point of the refrigerant is well beyond the outside temperature. The gas will cool until it reaches its boiling point, and then condense to a liquid as heat is absorbed by the outside air. The liquid refrigerant is then forced back through the expansion valve by the condenser pressure.

Refrigerant

2007-11-27T11:23:00.000-08:00

A liquid with a low boiling point must be used to make practical use of the heat transfer that occurs when a liquid boils. Refrigerant-12 (R-12) is the refrigerant that was universally used in automotive air conditioning systems. At normal temperatures, it is a colorless, odorless gas that is slightly heavier than air. Its boiling point at atmospheric pressure is -21.7°F (minus 6°C). If liquid R-12 is spilled into the open air, it would be seen for a brief period as a rapidly boiling, clear liquid.

R-12 was nearly an ideal refrigerant. It operated at low pressure and condenses easily at the temperature ranges found in automotive air conditioning systems. It is also non-corrosive, non-toxic (except when exposed to an open flame), and nonflammable. However, due to its low boiling point and the fact that it is stored under pressure, certain safety measures must be observed when working around the air conditioning system. Unfortunately it was discovered the carbo-floro-carbons (CFC's) which were chemicals in the same group as dichlorodifluoromenthane, which you know as R-12 or Freon were depleting the ozone layer of the atmosphere.

On December 31, 1995, CFC-12 production essentially ended in the U.S. However to avoid release into the atmosphere it is still legal to use the existing stockpiles of CFC-12.

The replacement for CFC-12 has been a non-CFC refrigerant R-134a. This has been used since the 1994 model year. Some of the older R-12 systems are being changed over to R-134a but this can be a costly and complicated process on some vehicles.

There is a third category for refrigerants that substitute CFC-12, these also contain ozone depleting HCFC's such as R-22, R142b, and R-124.

There are strict governmental regulations enforced by the clean air act of 1990 section 609. These include specific regulations for the use and handling of each of the three types of refrigerants.

Theory of Air Conditioning

2007-11-26T13:25:00.000-08:00

In order to understand how air conditioning works, it is necessary to understand several basic laws about the flow of heat. While it may seem puzzling to talk about heat in the same breath as air conditioning, heat is your only concern. An air conditioner does not cool the air, but rather, removes the heat from a confined space.

The law of entropy states that all things must eventually come to the same temperature; there will always be a flow of heat between adjacent objects that are at different temperatures. When two objects at different temperatures are placed next to each other, heat will flow from the warmer of the two objects to the cooler one. The rate at which heat is transferred depends on how large the difference is between their temperatures. If the temperature difference is great, the transfer of heat will be great, and if the temperature difference lessens, the transfer of heat will be reduced until both objects reach the same temperature. At that point, heat transfer stops.

Because of entropy, the interior of an automobile tends to remain at approximately the same temperature as the outside air. To cool an automobile interior, you have to reverse the natural flow of heat, no matter how thoroughly insulated the compartment might be. The heat which the body metal and glass absorb from the outside must constantly be removed.

The refrigeration cycle of the air conditioning system removes the heat from a vehicle's interior by making use of another law of heat flow, the theory of latent heat. This theory says that during a change of state, a material can absorb or reject heat without changing its temperature. A material is changing its state when it is freezing, thawing, boiling or condensing. Changes of state differ from ordinary heating and cooling in that they occur without the temperature of the substance changing, although they cause a visible change in the form of the substance. While many materials can exist in solid, liquid, or gaseous form, the best example is plain water.

Water is a common material that can exist in all three states. Below 32°F (0°C), it exists as ice. Above 212°F (100°C), at sea level air pressure, it exists as steam, which is a gas. Between these two temperatures, it exists in its liquid form.

Since a change in state occurs at a constant temperature, it follows that a material can exist as both a liquid and a gas at the same temperature without any exchange of heat between the two states. As an example, when water boils, it absorbs heat without changing the temperature of the resulting gas (steam).

The change from a solid to a liquid and vice versa is always practically the same for a given substance-32°F (0°C) for water-but the temperature at which a liquid will boil or condense depends upon the pressure. For example, water will boil at 212°F (100°C), but only at sea level. The boiling point drops slightly at higher altitudes, where the atmospheric pressure is lower. We also know that raising the pressure 15 lbs. above normal air pressure in an automobile cooling system will keep the water from boiling until the temperature reaches about 260°F (127°C)

One additional aspect of the behavior of a liquid at its boiling point must be clarified to understand how a refrigeration cycle works. Since liquid and gas can exist at the same temperature, either the evaporation of liquid or the condensation of gas can occur at the same temperature and pressure conditions. It's just a matter of whether the material is being heated or cooled.

As an example, when a pan of water is placed on a hot stove, the heat travels from the hot burner to the relatively cool pan and water. When the water reaches it's boiling point, its temperature will stop rising, and all the additional heat forced into it by the hot burner will be used to turn the liquid material into a gas (steam). The gas thus contains slightly more heat than the liquid material.

If the top of the pan were now to be held a couple of inches above the boiling water, two things would happen. First, droplets of liquid would form on the lower surface of the lid. Second, the top would get hot very quickly. The top becomes hot because the heat originally used to turn the water into steam is being recovered. As the vapor encounters the cooler surface of the metal, heat is removed from it and transferred to the metal. This heat is the same heat that was originally required to change the water into a vapor, and so it again becomes a liquid.

Since water will boil only at 212°F (100°C) and above, it follows that the steam must have been 212°F (100°C) when it reached the top and must have remained that hot until it became a liquid. The cooling effect of the top (which started out at room temperature) caused the steam to condense, but both the boiling and the condensation took place at the same temperature.

To sum up, refrigeration is the removal of heat from a confined space and is based on three assumptions:

Heat will only flow from a warm substance to a colder substance.
A refrigerant can exist as both a liquid and a gas at the same temperature if it is at its "boiling point." A refrigerant at its boiling point will boil and absorb heat from its surroundings if the surroundings are warmer than the refrigerant. A refrigerant at its boiling point will condense and become liquid, losing heat to its surroundings, if they are cooler than the refrigerant.
The boiling point of the refrigerant depends upon the pressure of the refrigerant, rising as the pressure rises and falling as the pressure falls. The operation of the refrigeration cycle illustrates how these three laws are put to use.

A/C Tips

2007-08-31T12:39:00.000-07:00

No air coming from air conditioning vents

Check the air conditioner fuse and replace as necessary.
Air conditioner system discharged. Have the system evacuated, charged and leak tested by an MVAC certified technician, utilizing approved recovery/recycling equipment. Repair as necessary.
Air conditioner low pressure switch defective. Replace switch.
Air conditioner fan resistor pack defective. Replace resistor pack.
Loose connection, broken wiring or defective air conditioner relay in air conditioning electrical circuit. Repair wiring or replace relay as necessary.

Air Conditioner blows warm air

Air conditioner system is discharged. Have the system evacuated, charged and leak tested by an MVAC certified technician, utilizing approved recovery/recycling equipment. Repair as necessary.
Air conditioner compressor clutch not engaging. Check compressor clutch wiring, electrical connections and compressor clutch, and repair or replace as necessary.

Water collects on the interior floor when the air conditioner is used

Air conditioner evaporator drain hose is blocked. Clear the drain hose where it exits the passenger compartment.
Air conditioner evaporator drain hose is disconnected. Secure the drain hose to the evaporator drainage tray under the dashboard.

Air conditioner has a moldy smell when used

The air conditioner evaporator drain hose is blocked or partially restricted, allowing condensation to build up around the evaporator and drainage tray. Clear the drain hose where it exits the passenger compartment

Compressor clutch problems

2007-08-31T12:34:00.001-07:00

If the compressor is not turning, make sure the magnetic clutch engages when energized. Underlying problems here may include a bad relay, fuse, wiring problem or a defective clutch. If the clutch fails to cycle on and off when the A/C is turned on, jumping the clutch lead with a jumper wire from the battery will show if the problem is in the clutch or elsewhere. If the clutch engages, the problem is the clutch power supply (relay, fuse, wiring, switch or control module). Refer to a wiring diagram and work backward toward the battery to find out why the voltage is not getting through.

Many A/C systems have a low-pressure cutout switch that prevents the compressor clutch from engaging if system pressure (the refrigerant charge) is too low. This is designed to protect the compressor from damage in the event of a leak. So if the clutch is not engaging, check the refrigerant charge and the cutout switch. The clutch air gap is also important for proper clutch operation. If the clearance is not correct, the clutch may slip and burn or not engage at all. The specs can be found in a service manual along with adjustment procedures. Generally speaking, most clutches call for a 0.015 to 0.040 inch press fit clearance.

Compressor Failure

2007-08-31T12:31:00.001-07:00

The compressor is the heart of the refrigeration circuit. It pumps and pressurizes the refrigerant to move it through the A/C system. Compressors work hard and run hot, up to several hundred degrees and several hundred pounds per square inch of internal pressure. They rely on only a few ounces of lubricant to keep their parts moving. If the lubricant is lost because of a leak, or the lubricant breaks down due to contamination, the compressor will not last. Sooner or later, the compressor will call it quits. The most common symptom of a compressor failure (besides no cooling) is a seized compressor. It will not turn when the magnetic clutch engages, and you may hear squeals of protest from the drive belt. Or, the belt may have already broken or been thrown off its pulleys.

Loss of lubrication is unquestionably the most common cause of compressor failure. This can happen when there is a refrigerant leak somewhere in the system that allows refrigerant and oil to escape. Typical leak points are hoses, hose and pipe connections (O-rings and flange gaskets), the evaporator, condenser or the compressor shaft seal. An electronic leak detector or dye should be used to find the leak so it can be repaired. A restriction inside the A/C system can also starve the compressor for oil. Oil circulates with the refrigerant, so if the orifice tube or expansion valve is blocked it may cause the compressor to run dry and seize.

Even if a compressor is still turning, it may have to be replaced if itï¿½s leaking, making excessive noise or not working correctly. Some compressors are naturally noisier than others, but loud knocking noises can sometimes be caused by air in the system (the cure here is to vacuum purge the system to remove the unwanted air, then to recharge the system with refrigerant). Metallic noises and bearing noise are usually signals that the compressor is about to fail. A new compressor may be needed if the unit is leaking internally or not producing enough pressure due to bad reed valves, worn piston rings, or worn or scored cylinders, etc.). A worn compressor or one with internal problems will not be able to develop normal operating pressures with a full charge of refrigerant. This kind of problem can be diagnosed with an A/C gauge set. Poor cooling can also be caused by a lot of things other than a bad compressor, so do not replace the compressor until you have ruled out other possibilities such as a low refrigerant charge, too much oil in the system, air contamination, a clogged condenser, plugged orifice tube, inoperative electric cooling fan, etc.

Compressor operation can be affected by sensors in vehicles with automatic temperature control systems. Some have an A/C pressure transducer (usually mounted in the high side line) to monitor refrigerant pressure and shut off the compressor if pressure gets too high; a compressor temperature sensor to turn off the compressor if it gets too hot; and/or a compressor rpm sensor to monitor belt slippage. Mitsubishi, for example, uses a "belt lock controller" to disengage the compressor if the drive belt slips or the compressor seizes. On 1996 and newer Mercedes-Benz E-Class cars, the A/C control module will disengage the compressor if the refrigerant temperature and pressure sensors do not show a rise when the compressor is being driven.

A/C Cooling Problem

2007-08-31T12:24:00.001-07:00

The most likely cause of an automotive air conditioner cooling problem is no refrigerant in the system. If the refrigerant has escaped past a leaky compressor or O-ring seal, leaked out of a pinhole in the evaporator or condenser, or seeped out through a leaky hose, the leak needs to be identified and repaired before the system is recharged.

On many systems, the compressor will not turn on if the refrigerant is low because the "low pressure safety switch" prevents the compressor clutch from engaging if system pressure is low. This protects the compressor from possible damage caused by a lack of lubrication.

One of the first things you should check, therefore, is compressor engagement. If the compressors magnetic clutch is not engaging when the A/C is turned on, the problem may be a blown fuse or a wiring problem. If the fuse is blown, replacing it may restore cooling temporarily. But the underlying reason for the fuse blowing in the first place needs to be identified and corrected to prevent the same thing from happening again.

If the magnetic clutch is receiving voltage but is not engaging the compressor, the clutch is defective and needs to be replaced. If there is any evidence of leakage around the compressor shaft seal, the seal should also be replaced.

If the clutch works but fails to turn the compressor (the belt may squeal in protest!), the compressor has seized and needs to be replaced.

Compressor failures are usually the result of loss of lubrication, which in turn may be due to low refrigerant in the system, a blockage (such as a plugged orifice tube which prevents refrigerant and oil from circulating to the compressor), loss of lubricant due to leaks or improper service procedures (not adding oil to the system to compensate for oil lost through leakage or component replacement), or use of the wrong type of lubricant.

R-12 systems require mineral oil while R-134a systems require various types of PAG oil or POE oil. Using mineral oil in a newer R-134a system can cause serious lubrication problems as can using the wrong grade (viscosity) of PAG oil. Always follow the vehicle or lubricant manufacturers compressor oil recommendations.

The next thing you should check when troubleshooting a no cooling problem is system pressure. For this, you need a set of A/C service gauges. Attach your service gauges to the high and low service fittings. If both the high and low side pressure gauges read low, the system is low and needs recharging. But before any refrigerant is added, check for leaks to find out where the refrigerant is going.

R134A Retrofit

2007-08-31T12:11:00.002-07:00

As long as R-12 is available, there is no real reason to convert older vehicles to R-134a. That is because R-12 systems cool best when charged with R-12 refrigerant. But converting to R-134a does make sense if your A/C system requires major A/C repairs (such as a new compressor, condenser or evaporator). The extra cost involved to make the changeover to R-134a does not add that much to the total repair bill.

A basic retrofit procedure can be done one of two ways. The "Type 1" retrofit follows the OEM recommended procedure and generally involves removing all the old mineral oil from the system, replacing the accumulator or receiver-drier with one that contains a desiccant (X-7) which is compatible with R-134a, replacing O-rings (if required), installing or replacing a high pressure cutout switch and/or orifice tube (if required), then adding the specified PAG oil and recharging the system with R-134a. Federal law also requires the installation of R-134a fittings on the high and low service ports to reduce the chance of refrigerant cross-contamination the next time the vehicle is serviced, and labels that identify the system has been converted to R-134a. For more information, see the R134A retrofit guide program featured on this web site.

A "Type 2" procedure is more of a "quick and cheap" approach to retrofit. On many 1989 through 1993 vintage vehicles, the R-12 A/C systems can be converted to R-134a by simply recovering any of the R-12 that is left in the system (NOTE: it is illegal to vent refrigerant into the atmosphere!), adding POE oil (which is compatible with both types of refrigerant), and then recharging with R-134a.

NOTE: Type 2 conversions cannot always be done on some vehicles because their compressors may not be compatible with R-134a (any compressor with Viton seals has to be replaced). This includes original equipment compressors such as Tecumseh HR980, some Keihin compressors and some Panasonic rotary valve style compressors in older Nissan vehicles.

Durability is another concern. Because R-134a raises compressor discharge pressures and increases the compressors work load, some lightweight compressors may not be rugged enough to tolerate R-134a over the long haul. This applies to the Harrison DA6 and Ford FX-15 compressors. The Harrison DA6 can be replaced with a HD-6, HR-6 or HR-6HE compressor. The Ford FX-15 compressor can be replaced with a FS-10 compressor.

A/C Flushing

2007-08-31T12:11:00.001-07:00

If the compressor has failed, or the system is full of sludge or contamination, the condenser, evaporator and hoses should all be flushed with an approved flushing chemical (such as Dura 141b) to clean the A/C system. Flushing can help prevent repeat compressor failures and system blockages by dislodging and cleaning out sludge and debris. Replacing badly contaminated parts such as the condenser, accumulator or receiver-drier and orifice tube or expansion valve is another way to get rid of these contaminants, but flushing is usually a more practical and economical choice. Regardless of which approach you use, the orifice tube or expansion valve should always be replaced when contamination is found.

NOTE: Some types of compressors can be very difficult to flush completely. These include "parallel" flow condensers and those with extremely small passageways. If contaminated, these types of condensers must be replaced to reduce the risk of a repeat compressor failure. Installing ain in-line filter is also recommended for added insurance,

When a compressor fails, a lot of metallic debris is often thrown into the system. Most of this debris collects in the condenser where it can cause blockages that reduce cooling performance. If the debris is carried through the condenser and enters the liquid line, it can plug the orifice tube or expansion valve. This can block the flow of refrigerant and lubricating oil causing a loss of cooling and possible compressor damage. Debris can also migrate backwards from the compressor through the suction hose causing blockages in the accumulator or receiver-drier.

Another source of trouble can be debris from old hoses that are deteriorating internally. Tiny flakes of rubber can be carried along to the orifice tube or expansion valve and cause a blockage.

Sludge is usually the result of moisture-contamination. The blackish goo that results can damage the compressor and plug the orifice tube or expansion valve. The moisture-absorbing "desiccant" in the accumulator or receiver-drier is supposed to prevent this from happening. But the desiccant can only hold so much moisture. Once saturated, sludge begins to form. So you should also replace the accumulator or receiver-drier if the system is contaminated, has leaks or must be opened up for repairs.

Another reason for flushing is to remove residual lubricating oil from the system. This should be done when retrofitting an R-12 system to R-134a. It should also be done if the lubricating oil is contaminated or the system contains the wrong type of oil for the application. Flushing out the old oil can prevent oil overcharging, reduced cooling performance and/or lubrication incompatibility problems.

For added insurance after flushing, you can install a high side filter to protect the orifice tube or expansion valve from any residual debris that might still be in the system, and/or a second filter in the suction hose to protect the compressor.

Noise

2007-08-31T12:10:00.001-07:00

Noise from the compressor usually means the compressor is on its way out. But noise can also be caused by cross-contaminated refrigerant (operating pressure too high), air in the system or the wrong type of compressor lubricant.

Noise can also be caused by hoses or other parts rattling against other components in the engine compartment. Check the routing of the hoses, support brackets, etc., to pinpoint the noise.

Intermittent cooling

2007-08-31T12:08:00.002-07:00

An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.

Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.

For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.

Air can get inside a system through leaks, by not evacuating the system prior to recharging it, and/or by recharging the system with refrigerant that¿½s contaminated with air. Recovery equipment can suck air into the recycling tank if an A/C system contains air or if the system has a leak. For this reason, the refrigerant recovery tank on recycling equipment must be checked and purged daily. On some equipment, this is done automatically. But on equipment that lacks an automatic purge cycle, tank pressure and temperature has to be measured and compared to a static pressure reference chart.

Some refrigerant identifier equipment can detect air in the system as well as other contaminants. You should always use an identifier to check the refrigerant before servicing the system to prevent cross-contamination of your recovery and recycling equipment.

Refrigerant leaks

2007-08-31T12:08:00.001-07:00

All vehicles leak some refrigerant past seals and through microscopic pores in hoses. The older the vehicle, the higher the rate of seepage. Newer vehicles have better seals and barrier style hoses so typically leak less than a few tenths of an ounce of refrigerant a year. But system capacities also tend to be smaller on newer vehicles, so any loss of refrigerant will have more of an adverse effect on cooling performance.

Various methods can be used to check for leaks. The telltale oil stains and wet spots that indicate leaks on older R-12 systems are less apparent on the newer R-134a systems because PAG lubricants are not as "oily" as mineral oil. This makes it harder to see leaks.

Leaks can be found by adding special dye to the system (available in pressurized cans premixed with refrigerant), an electronic leak detector, or plain old soapy water (spray on hose connections and watch for bubbles -- requires adding some refrigerant to system first and turning the A/C on). Once you've found a leak, repairs should be made prior to fully recharging the system. Most leak repairs involve replacing O-rings, seals or hoses. But if the evaporator or condenser are leaking, repairs can be expensive.

Audi A/C System

2007-08-27T13:45:00.001-07:00

In future, it will be possible to use this modular A/C system in other Audi models, in addition to the A5. “Audi and Behr collaborated on the initial design a full year before the order was placed. We were able to convince the customer of the benefits of our modular system”, explains Thomas Reimet, Audi Air Conditioning Project Manager at Behr.
Behr has developed a modular design concept for the fully automatic climate control system, which can be expanded from one climate zone to up to four. Behr realized a new mixing concept on very little installation space. The three-zone A/C system replaces the separate rear HVAC module and provides air conditioning to the rear of the vehicle, independent of the settings for driver and front seat passenger. Behr produces the climate control unit in its plant in Neustadt on the Danube. Many of the housing components are manufactured using the MuCell injection molding process. This means less weight and higher resistance to distortion. In the diesel variant, Behr has integrated a new generation PTC auxiliary heater.

For the engine cooling system in the new A5, Behr is supplying both the 80 and the 64mm deep charge air coolers, as well as a variant of the main radiator for passenger vehicles equipped with the basic engine model. The special feature of the charge air cooler, which was developed in Stuttgartand produced by Behr Czech, is the 30 percent reduction in tank-header overhang (from 9 to 6mm). This was achieved by using for the first time a modified header piercing and sealing concept for passenger car charge air coolers. “Implementing the new design presented major challenges for all concerned”, admits Peter Frisch, Behr Project Manager Audi, Engine Cooling, C-VW. “However, the design was successfully brought to production maturity thanks to close collaboration and consultation with the customer”. This particular strength was one of the key reasons for Behr being awarded the contract.

VW Air Conditioners

2007-08-27T13:43:00.001-07:00

One of the most known brands in automobile industry is Volkswagen. It is famous for its great performance, efficiency, stylish looks and comfortable features. Volkswagen air conditioning system plays key role in offering its occupants enjoyable and pleasurable ride. Functioning of air conditioning system comprises of high quality and efficient components, such as compressor, condenser, evaporator, receiver-drier and orifice tube.

Volkswagen AC receiver-drier is one of the major components of air conditioning system. It is also known as accumulator. It is usually used on the high side of system, where thermal expansion valve is used. Liquid refrigerant is needed by such metering valve. A receiver is also used to ensure that valve is getting liquid refrigerant or not. The major function of receiver-drier is the separation of gas and liquid. It also eliminates moisture and removes the dirt completely. On the top of Volkswagen AC receiver-drier there is one sight glass. This sight glass is used for the charging of system. When the Volkswagen AC system will function appropriately, you cannot see any vapor bubbles in the sight glass. Whenever the system is empty, you must change the receiver-drier.

Volkswagen AC compressor is also known as the heart of air conditioning system. In case, the Volkswagen AC compressor is seized, then it indicates a worn out compressor. Drive belt will start making squealing sounds. After being engaged by magnetic clutches, Volkswagen AC compressor would be unable to move. Major cause for the failure of Volkswagen AC compressor is the inadequacy of lubrication. Lack of lubrication may also occur due to leakage of refrigerant in the system. There are a few common leakage points, such as hoses, hose and pipe connections, evaporator, condenser or compressor shaft seal.

You must perform a regular check up for the adequate performance of vehicle. If you are looking for a reliable and authenticated site for the components of Volkswagen Air conditioning system then log on to autopartsfair.com. Autpartsfair.com comprises of huge inventory of Volkswagen A/C system. Just browse through its extensive range and order the required part. Autopartsfair.com offer Volkswagen air conditioning system at reasonable prices. If you are worried about the quality of Volkswagen AC parts available at autopartsfair.com then there is no need to worry. These parts have met original manufacturer specification. Moreover, autopartsfair.com offer warranty coverage plan with Volkswagen AC parts. So, do not waste time and order the required part now. If you have any query regarding the product, you may call the customer care unit.

Mercedes Benz A/C System

2007-08-27T13:34:00.000-07:00

Mercedes Benz has always been associated with rich and famous. They are popular for incorporating finest engineering and craftsmanship. Thus, results in high manufacturing costs. Air conditioning system equipped in Mercedes Benz is one of the major factors for comfortable and pleasurable ride. There are five major components that plays key role in the effective performance of the Mercedes Benz AC system. They are Mercedes Benz compressor, Mercedes Benz refrigerant, Mercedes Benz condenser, Mercedes Benz expansion valve and Mercedes Benz drier or evaporator.

During air conditioning process, refrigerant is placed under pressure by the compressor and sent to condensing coils. These coils are usually present in front of radiator. After compression, gas heats up a lot. Later, gas condenses into liquid and this change turn it hotter. Now, lots of heat is lost by refrigerant followed by sending liquid to evaporator.

On the high side of AC system, Mercedes Benz receiver drier or Accumulator is used. A thermal expansion valve is used by the Mercedes Benz receiver-drier. Liquid refrigerant is required by such metering valve. In order to ensure that valve is getting liquid refrigerant a receiver is also used. Separation of gas and liquid is the major function of receiver-drier.

Mercedes Benz AC receiver-drier also eliminates moisture and filters out dirt. A sight glass is also mounted on the top of Mercedes Benz AC receiver-drier or accumulator. Sight glass usually charges system. If the air conditioning system is working appropriately then vapor bubbles will not be visible in sight glass.

When the system is empty, it would be advisable to change Mercedes Benz receiver-drier or accumulator. You must change it after three years as desiccant pellets break down. Thus, results in clogging of expansion valve. This will make the system inoperable and compressor will be damaged.

A regular check up is essential for the adequate working of Mercedes Benz AC system. If any of the Mercedes Benz AC components is not worn out then repair or replace it immediately. High quality Mercedes Benz AC parts are available at autopartsfair.com. Autopartsfair.com offer huge range of high quality parts in varied range and styles. You may browse through the extensive range of parts available at autopartsfair.com. These high quality Mercedes Benz AC parts are available at discounted prices. Mercedes Benz AC parts available at autopartsfair.com are reliable and durable, as they have met original manufacturer specification. Autopartsfair.com also offers significant installation and maintenance tips for Mercedes Benz AC parts. Just log onto auatopartsfair.com and order the required part now.

Mercedes M-Class Model 163 climate control system '98 to '01

2007-08-27T13:31:00.000-07:00

The heating, ventilation, and A/C (HVAC) system in the M-Class has semiautomatic temperature regulation and manual control over the air source and distribution. The temperature control is achieved without the use of a heater valve, also called mono valve in other models. The M-Class heater core is thus always hot, at about 87 deg C.

Air Conditioning Switch

The On/Off switch connects to the A/C control module (N19), which, through the All Activity Module (N10) controls the activation of the air conditioning compressor clutch. The A/C compressor operates only when the engine is running and the blower motor is switched on. The AAM (N10) also uses other information from the CAN to choose when to operate the compressor clutch, i.e. engine temperature.

Air Temperature Control

An NTC resistor behind a grille below the low range switch senses the in-cabin temperature. A hose connects it to the main climate box thus drawing air across the sensor.

Air temperature is controlled by a variable resistor rotary control. Signals from the resistor to the amplifier determine the desired interior temperature output of the system. A switch at detent position at the full counter clockwise (maximum cooling) position overrides the air recirculation switch to close the fresh air door for maximum interior cooling (with A/C on).

Air Distribution Control

The switch contains 12 detents for air distribution. A cable operates air distribution doors to direct air flow in the air distribution system to the air flow outlets. The air flow outlets are:

Front windshield defroster/side window.
Face outlets.
Foot outlets.

Air flow from the above outlets depends on the position of this switch and the center air outlet control wheel above the temperature control panel.

Blower Motor Switch

Off and 4 blower motor speeds are available. Switch must be in position 1-2-3 or 4 for temperature system to provide either heated or cooled air. The switch is an input to the amplifier (N19). The logic circuit in the amplifier directs system voltage to the relay/blower motor resistor (R14) for reduced blower speeds (positions 1-2-3). The switch bypasses the resistor for the highest blower speed (position 4).

Fresh/Recirculation (FRS/REC) Switch

The switch selects the air to circulate either interior air or fresh outside air. The On/Off switch controls the air door motor which is linked to the door.

Air Conditioning/Heating Control Module (N19)

The A/C Amplifier (N19) is the control unit for the heating and air conditioning system. The A/C control module senses input signals from the various components and then determines if conditions are met for proper operation. The A/C control module then outputs control signals to energize various actuators directly or signals the AAM (N10).

The A/C control module receives input information from the following devices:

Air conditioning switch.
Interior air temperature sensor (NTC resistor below low range switch).
Temperature selector control.
Blower switch control.
Evaporator temperature sensor.
Air mixture flap door position signal.

The A/C Control Module sends control signals to the following devices:

Air mix damper door motor.
AAM (N10).
Fresh/Recirculation (FRS/REC) door motor.

All Activity Module (AAM) (N10)

The AAM determines if certain conditions are met for the air conditioning/heating operation.

It receives input from the following devices:

Hi-Low pressure sensor (via CAN).
Engine coolant temperature sensor (via CAN).

Sends control signals to the following devices:

Air conditioning compressor clutch.
Condensor fans via relay.
Relay K21 to power the blower motor.

A/C Compressor

The Denso A/C compressor is a 7 cylinder variable pitch swash plate design similar to the model 210 (E-Class). It is driven by a serpentine belt from the engine crankshaft and activated by an electric clutch controlled by the AAM. If it doesn't come on it might be a bad/lose connection on the underside of the fuse box sometimes at connector M/A pin 2.

Air Mix Damper Door

The mechanical door is controlled by a linkage from the servo electric motor. The door covers/uncovers the air passage through the heater core to mix heated and cool air in correct proportion needed to achieve desired interior temperature. A feed back potentiometer sends a signal to N19 (controller) for door position.

System Operation

Air Flow

Outside or interior air for the HVAC system depends on the position of the FRS/REC (air recirculation) switch.

The blower motor provides air flow through the system. If the blower switch is OFF, there is no air flow through the system. With the switch ON, air flows from the blower motor into an air filter before passing through the evaporator fins into the air distribution housing.

A moveable air mix damper door directs air around and/or through the heater core on its way to the air distribution ducts.

The quantity and proportion of air through each air distribution duct depends on the settings of the air distribution switch on the control panel.

Air Temperature, Cool

If maximum cool air is needed (A/C ON), the air mix damper door directs all cold air around, not through, the heater core.

The air temperature sensor provides a reference temperature midpoint setting of 68 deg F. During system operation, the temperature switch setting, relative to this reference point, will cause the air mix damper door to move and regulate the air temperature accordingly.

When the temperature control is set for maximum cooling, the outside door closes in order to increase the performance of the system.

Air Temperature, Hot

When the A/C switch is OFF and maximum hot air is needed, the air mixture damper door directs all air through the heater core.

Air Temperature, Warm

When warm air is needed, the air mix damper door moves to direct air around and through the heater core to arrive at the desired air temperature setting.

A/C System for Sprinter and Crafter

2007-08-27T13:29:00.001-07:00

Behr, a specialist for car and truck air conditioning and engine cooling systems, and Behr Hella Thermocontrol,(BHTC), the Behr-Hella joint venture specializing in climate control, in collaboration with DaimlerChrysler, have developed the air conditioning system for the new Mercedes-Benz Sprinter and the VW Crafter. Birgit Kelm, head of Truck Customer Projects at Behr, emphasizes the company’s level of involvement: "We not only took responsibility for implementing the air conditioning system itself, but also provided customer support in our role as consultant and systems integrator. We combined all the HVAC components into a single system, irrespective of whether the components came from us or from another manufacturer.”

The Mercedes-Benz Sprinter and the VW Crafter, developed in a joint project by DaimlerChrysler and VW, both have a standard heating system and the optional "Tempmatik” air conditioning system. When the temperature is adjusted manually, Tempmatik automatically factors in the temperatures of the vehicle cabin, outside air, evaporator, and coolant, and uses this data to compute the ideal comfort climate. The blower speeds, too, are controlled as a function of the outside temperature, the vehicle speed, and the roof height of the interior. The control head for the heating and air conditioning system can be supplied in a total of 18 variants.

"The front seat air conditioning with the control head forms the control center for the HVAC system and is housed in the center section of the cockpit. ” continues Birgit Kelm.

"In the Sprinter, this air conditioning system can be supplemented with two alternative roof-mounted cooling systems if the vehicle is to be used for passenger transport. That way, passengers in the second and third seated rows also enjoy a high level of climate comfort.”

The heating and air conditioning system can be individually tailored to the application location and the intended use, since different air conditioning is required in hot countries compared with that in countries with temperate climates. It is also important whether the vehicle is to be used as a delivery van or for passenger transport. If the Sprinter is used for passenger transport, the auxiliary cooling system is suitable in temperate climates. This simply consists of an additional evaporator, and is integrated into the basic refrigerant circuit (this roof-mounted cooling system is also available for the Crafter). If the Sprinter is used in regions with extreme climate conditions, the more powerful system with a separate refrigerant circuit is recommended. Behr has designed both roof-mounted cooling systems in such a way that they fit into the gap in the roof intended for the sliding roof. This represents an advantage over standard roof-mounted climate control modules, which are normally housed on the roof at the rear, since, in addition to the more compact construction, the lines for the refrigerant are shorter and easier to integrate.

Mercedes Benz Air Conditioning Compressor

2007-08-27T13:25:00.000-07:00

First of all, some compressors just wear out. You put a bazillion miles on them and their time is just simply up. However, the majority of the time the compressor fails is from lack of proper maintenance or the result of poor service procedures.

Let's remember that most of the A/C compressors that Mercedes Benz have used do not carry their own on board oil supply. The refrigerant oil is delivered throughout the system via the refrigerant.

Just as you would not run your engine without oil people attempt to run the air conditioning compressors without oil. How does this happen? Underneath the hood of your car is a pretty hostile environment subject to all kind of heat, cold, and vibration. Over time refrigerant may be lost through the various seals and out the front of the compressor. Since the refrigerant carries the oil it stands to reason that when you lose refrigerant you lose the oil at the same time. If you fail to replace the oil when you add new refrigerant you might as well log on and start pricing a new compressor. If you are not doing the job yourself, do not assume that refrigerant oil has been added. You must ask and make sure. It will be cold when you pick it up but not for long.
Preventive maintenance goes a long way. When you open the hood do a visual inspection of your Mercedes air conditioning system. Check your air conditioning hoses, Mercedes compressor, and Mercedes condenser for signs of leaks, that is oil residue at any of the joints or on the parts. Failure to repair the problem may damage or destroy the compressor since you are losing the oil that lubricates the moving parts of the air conditioning system.
If your Mercedes air conditioner is not working properly do not use it until you can check it out. This may prevent further damage. Remember that your compressor turns on when you turn on the defroster too so do not assume that it can wait till spring to have it repaired.

BMW Air Conditioners

2007-08-27T13:17:00.000-07:00

Air conditioner equipped in BMW usually serves the purpose of refrigerator. It transfers heat from one place to another. BMW air conditioner is equipped with five major components. They are compressor, refrigerant, condenser, expansion valve and dryer or evaporator. Refrigerant in the system is compressed by BMW compressor. BMW refrigerant carries away the heat. When the compressed refrigerant passed through the BMW condenser, the condenser turns hot. BMW expansion valve serve the purpose of nozzle. Heat to the refrigerant is added by the BMW evaporator or dryer. In this manner, BMW air conditioner works.

BMW air conditioner clutch plays key role in electric engaging and disengaging. It works according to the commands from air conditioner system. Air conditioner electro-magnetic clutch is usually mounted at the front of air conditioning compressor. Designing of the air conditioner by different manufacturer may vary. The BMW air conditioning has been divided into two major sides. They are high-pressure and low-pressure. High pressure side is connected to the outlet or the discharge, whereas low pressure side is connected to inlet of the compressor.

The major purpose of BMW air conditioner clutch is to energize and lock clutch to compressor on command. After getting engaged, A/C compressor is driven by a serpentine belt or V-belt from engine.

BMW air conditioner compressor is also referred as heart of the air conditioning system. It is usually a belt driven pump tightened with the engine. It compresses and transfers the refrigerant gas. BMW air conditioning is divided into two major parts. They are high pressure side and low pressure side, also known as discharge and suction. As BMW air conditioner compressor is usually a pump, it must be comprised of intake side and discharge side. The refrigerant gas is drawn from BMW evaporator outlet by the intake or suction side.

The refrigerant is compressed and sent to air conditioner condenser after getting drawn. Now, refrigerant transfers the heat absorbed by the vehicle to BMW condenser. If you are facing problems regarding poor cooling or seized or noisy compressor then you must take your vehicle to expert technician. Wrong refrigerant oil is also one major cause for improper functioning AC.

Replace or repair the worn out BMW AC part for effective working of the air conditioning system. If you are looking for high quality parts then log on to autopartsfair.com. Autopartsfair.com offer high quality parts at discounted price. There is no need to bother about the durability and reliability of the parts available ay autoparstfair.com, as they are OEM certified.

BMW Automatic air conditioning

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Enjoy a comfortable temperature and a pleasant environment in your BMW's cabin with automatic air conditioning. Thanks to its intuitive usability and individually adjustable settings for you and your passenger, you're assured of a pleasant atmosphere at all times.

When activated, the automatic climate control system channels fresh air from outside the vehicle, cools it, reduces its humidity and, depending on the temperature setting, warmed again. Air temperature, air volume and air quality can be precisely controlled, whether the system is operating in manual or automatic mode. In automatic mode, the distribution of air flows and air volume is controlled automatically, and the temperature is held steadily at your selected temperature.
The CFC-free automatic air conditioning system also offers a range of additional features. Both driver and passenger can set individual preferences for air temperature. There are separate air channels for front and rear seats, plus an outlet in the B columns. The central console offers a temperature-controlled stowage space. The "maximum cooling" setting quickly cools the cabin on a sunny day. And even when the engine is not running, the automatic air conditioning system can be used to keep the cabin comfortable.
All control elements for the automatic air conditioning are positioned centrally, in easy reach of both driver and passenger. Depending on the model of your BMW, the iDrive and Control Display can also be used to change settings. The Car Memory feature saves your preferred settings and returns the system to these settings next time your drive your BMW.

Models that use this technology:

X5
Z4 Coupé
Z4 Roadster
Z4 M Coupé
Z4 M Roadster
M3 Coupé
M3 Convertible
M5 Sedan
M5 Touring
M6 Coupé
M6 Convertible

BMW A/C Condensers

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BMW has always been a brand of performance. “The Ultimate Driving Machine”—that has always been the name by which each and every vehicle that the company produces is marketed. For this reason, avid customers of BMW wouldn’t expect anything less than a performance vehicle from the company; and so far, the company hasn’t failed their expectations.

BMW vehicles, however, are not only about performance, although no one can deny the exhilaration that can be brought by the performance of every BMW to its owner. BMW vehicles are also about comfort, with a wide array of features that can make every powerful ride enjoyable. And how else can one best describe comfort inside a BMW vehicle than by describing its excellent air conditioning system, composed of only high quality A/C parts like the BMW A/C condenser.

The A/C condenser is that part of your vehicle’s air conditioning system responsible for radiating all the heat the A/C system has absorbed. The refrigerant enters the vehicle’s A/C condenser as a hot gas after absorbing much of the heat inside the vehicle’s cabin. With the aid of the engine fan, and other auxiliary fans that may be installed under the vehicle’s hood, the condenser cools the refrigerant and condenses it into a cooler, high-pressure liquid. Once cooled and liquefied, it is then pumped back into the other parts of the air conditioning system.

You can easily locate your BMW’s A/C condenser inside the engine compartment of your car. It is usually located in front of the radiator, unless otherwise there has been a modification made with your car and the A/C condenser was moved into another location for aerodynamic purposes. Nonetheless, it is still easily identifiable for it looks like the radiator, although only smaller. For front-wheel drive cars, the A/C condenser is cooled by one or more auxiliary fans instead of the engine fan.

BMW AC Compressor

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When we are driving, we usually want to experience the same level of comfort that we are used to at home and at our workplace. Thanks to the introduction of the automobile air conditioning system, many things have changed especially when it comes to comfort and luxuriousness offered by the vehicle’s interior. The vehicle’s air conditioning system is the one responsible for blowing cool air to the passenger cabin. Basically, there are three different types of air conditioning system found in the vehicles today. Though they have differences the concept and design of these ac systems are very similar to one another.

The most common components that can be seen in the automobile’s ac system are condenser, compressor, evaporator, thermal expansion bulb, orifice tube, receiver-drier and accumulator. If your vehicle possesses an orifice tube, it will not come with a thermal expansion valve because these two components have similar function. Likewise, a vehicle can have either an accumulator or a receiver-dryer but not both.

Your BMW ac compressor is considered as the heart of the car’s air conditioning system. It is a mechanical pump driven by a belt that’s attached to an engine. BMW AC compressor pumps the refrigerant to make it flow in a closed loop throughout the air conditioning system. The performance of the AC system is greatly affected by the performance of the ac compressor. When the engine starts to move, the BMW AC compressor would also start doing its job which is to take in the refrigerant from the low pressure side of air conditioning system. While inside the BMW AC compressor, the refrigerant is compressed into a high pressure and high temperature gas. And the compressed refrigerant will be passed on to the condenser, the system’s high pressure side.

The BMW ac compressor is really vital in your BMW ac system. Without it the ac system will surely not function. So if ever your BMW AC compressor got damaged have it replaced immediately or else the interior comfort of your car will be compromised. Finding a replacement BMW ac compressor isn’t that hard these days because they are available in most auto-part store in the automotive market.

A/C System Overview

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There are three primary components in a vehicle’s air conditioning system including the compressor, condenser, and evaporator. These parts are connected by tubes and hoses to form a continuous path with two distinct sections: a high-pressure side and a low-pressure side. In order to transfer heat from the vehicle’s interior to the outside air, a chemical refrigerant is circulated throughout the system. In theory, the A/C system accomplishes the same task as the engine’s cooling system, in that both absorb the heat from one area and release it to another (heat transfer). While coolant remains a liquid during the heat transfer process however, refrigerant repeatedly alternates between a liquid and a gas as it circulates throughout the air conditioning system.


Orifice tube air conditioning systems regulate refrigerant flow to the evaporator using a fixed metering device (orifice tube).	In an expansion valve air conditioning system, refrigerant flow to the evaporator varies according to the pressure in the suction line (evaporator outlet). This is detected by a sensing bulb mounted on the line, and relayed to the expansion valve via a capillary tube

The Refrigerant Cycle

The refrigerant cycle involves a three-step process that includes pressurization, condensation, and vaporization. Starting at the compressor, let’s identify these steps as we trace the flow of refrigerant through the system. The refrigerant enters the compressor through the suction port as a low-pressure vapor. After squeezing this vapor into a confined area (pressurization), it is released through the compressor’s discharge port. By pressurizing the refrigerant, the compressor causes the refrigerant vapor to become much hotter than the outside air. This ensures that it will change to a liquid as the cycle enters the next phase.

Once pressurized, the compressor pumps the high-pressure refrigerant vapor to the condenser, which is located directly behind the grille in front of the radiator. As outside air is drawn over the condenser by the engine fan, or forced past it by the ram-air effect, the incoming air absorbs the heat contained in the high-pressure vapor. This causes the vapor to condense into a high-pressure liquid, completing the second phase of the process (condensation).

As the refrigerant leaves the condenser, it makes its way toward the evaporator, which is located within the air hadling case along with the blower. Before entering the evaporator, the refrigerant flows through a metering device. This results in a significant drop in pressure, allowing the refrigerant to vaporize at a lower temperature. This ensures that the refrigerant will absorb the maximum amount of heat as the blower forces warm air over the evaporator. At this point, the vaporization phase is complete, and the heat-laden vapor is drawn back into the compressor so the cycle can be repeated.

Since heat is removed from the air during the vaporization phase, the air exits the panel vents at a much lower temperature. This not only results in cool air, but dehumidified air as well. Remember, warm air has high moisture content. Consequently, when the warm air comes in contact with the cold evaporator, the moisture condenses on the evaporator surface and eventually drains onto the ground. This is why a puddle of water forms under the car after it has been shut off with the air conditioner on.

Compressor

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Commonly referred to as the heart of the system, the compressor is a belt driven pump that is fastened to the engine. It is responsible for compressing and transferring refrigerant gas.

The A/C system is split into two sides, a high pressure side and a low pressure side; defined as discharge and suction. Since the compressor is basically a pump, it must have an intake side and a discharge side. The intake, or suction side, draws in refrigerant gas from the outlet of the evaporator. In some cases it does this via the accumulator.

Once the refrigerant is drawn into the suction side, it is compressed and sent to the condenser, where it can then transfer the heat that is absorbed from the inside of the vehicle.

Condenser

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This is the area in which heat dissipation occurs. The condenser, in many cases, will have much the same appearance as the radiator in you car as the two have very similar functions. The condenser is designed to radiate heat. Its location is usually in front of the radiator, but in some cases, due to aerodynamic improvements to the body of a vehicle, its location may differ. Condensers must have good air flow anytime the system is in operation. On rear wheel drive vehicles, this is usually accomplished by taking advantage of your existing engine's cooling fan. On front wheel drive vehicles, condenser air flow is supplemented with one or more electric cooling fan(s).

As hot compressed gasses are introduced into the top of the condenser, they are cooled off. As the gas cools, it condenses and exits the bottom of the condenser as a high pressure liquid.

Evaporator

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Located inside the vehicle, the evaporator serves as the heat absorption component. The evaporator provides several functions. Its primary duty is to remove heat from the inside of your vehicle. A secondary benefit is dehumidification. As warmer air travels through the aluminum fins of the cooler evaporator coil, the moisture contained in the air condenses on its surface. Dust and pollen passing through stick to its wet surfaces and drain off to the outside. On humid days you may have seen this as water dripping from the bottom of your vehicle. Rest assured this is perfectly normal.

The ideal temperature of the evaporator is 32° Fahrenheit or 0° Celsius. Refrigerant enters the bottom of the evaporator as a low pressure liquid. The warm air passing through the evaporator fins causes the refrigerant to boil (refrigerants have very low boiling points). As the refrigerant begins to boil, it can absorb large amounts of heat. This heat is then carried off with the refrigerant to the outside of the vehicle. Several other components work in conjunction with the evaporator. As mentioned above, the ideal temperature for an evaporator coil is 32° F. Temperature and pressure regulating devices must be used to control its temperature. While there are many variations of devices used, their main functions are the same; keeping pressure in the evaporator low and keeping the evaporator from freezing; A frozen evaporator coil will not absorb as much heat.

Orifice Tube

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The orifice tube, probably the most commonly used, can be found in most GM and Ford models. It is located in the inlet tube of the evaporator, or in the liquid line, somewhere between the outlet of the condenser and the inlet of the evaporator. This point can be found in a properly functioning system by locating the area between the outlet of the condenser and the inlet of the evaporator that suddenly makes the change from hot to cold. You should then see small dimples placed in the line that keep the orifice tube from moving. Most of the orifice tubes in use today measure approximately three inches in length and consist of a small brass tube, surrounded by plastic, and covered with a filter screen at each end. It is not uncommon for these tubes to become clogged with small debris. While inexpensive, usually between three to five dollars, the labor to replace one involves recovering the refrigerant, opening the system up, replacing the orifice tube, evacuating and then recharging. With this in mind, it might make sense to install a larger pre filter in front of the orifice tube to minimize the risk of of this problem reoccurring. Some Ford models have a permanently affixed orifice tube in the liquid line. These can be cut out and replaced with a combination filter/orifice assembly.

Expansion Valve

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Another common refrigerant regulator is the thermal expansion valve, or TXV. Commonly used on import and aftermarket systems. This type of valve can sense both temperature and pressure, and is very efficient at regulating refrigerant flow to the evaporator. Several variations of this valve are commonly found. Another example of a thermal expansion valve is Chrysler's "H block" type. This type of valve is usually located at the firewall, between the evaporator inlet and outlet tubes and the liquid and suction lines. These types of valves, although efficient, have some disadvantages over orifice tube systems. Like orifice tubes these valves can become clogged with debris, but also have small moving parts that may stick and malfunction due to corrosion.

Receiver-Drier

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The receiver-drier is used on the high side of systems that use a thermal expansion valve. This type of metering valve requires liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver is used. The primary function of the receiver-drier is to separate gas and liquid. The secondary purpose is to remove moisture and filter out dirt. The receiver-drier usually has a sight glass in the top. This sight glass is often used to charge the system. Under normal operating conditions, vapor bubbles should not be visible in the sight glass. The use of the sight glass to charge the system is not recommended in R-134a systems as cloudiness and oil that has separated from the refrigerant can be mistaken for bubbles. This type of mistake can lead to a dangerous overcharged condition. There are variations of receiver-driers and several different desiccant materials are in use. Some of the moisture removing desiccants found within are not compatible with R-134a. The desiccant type is usually identified on a sticker that is affixed to the receiver-drier. Newer receiver-driers use desiccant type XH-7 and are compatible with both R-12 and R-134a refrigerants.

Accumulator

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Accumulators are used on systems that accommodate an orifice tube to meter refrigerants into the evaporator. It is connected directly to the evaporator outlet and stores excess liquid refrigerant. Introduction of liquid refrigerant into a compressor can do serious damage. Compressors are designed to compress gas not liquid. The chief role of the accumulator is to isolate the compressor from any damaging liquid refrigerant. Accumulators, like receiver-driers, also remove debris and moisture from a system. It is a good idea to replace the accumulator each time the system is opened up for major repair and anytime moisture and/or debris is of concern. Moisture is enemy number one for your A/C system. Moisture in a system mixes with refrigerant and forms a corrosive acid. When in doubt, it may be to your advantage to change the Accumulator or receiver in your system

Retofit Procedure

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1. Evacuate the R-12, if there is any left in the system. By law, this must be done without venting (releasing the gas into the atmosphere) by a certified mechanic using approved R-12 Recovery equipment. Many installers will do this without charge, because the R-12 they recover from your system is valuable
	2. Attach Adaptor to the low-pressure port: The low-pressure port usually has a blue or black dust cap and is located on the larger diameter tubing that runs between the evaporator (in the dashboard) and the compressor (see FAQ, "How do I find the low-pressure port?"). Remove the dust cap . Attach the adapter to the low-pressure port.
	3. Charge the System & Measure Pressure: Assemble the hose and refrigerant can. Be sure the engine is operating and the A/C is set to maximum cooling. Connect the hose to the low-pressure port and preceed to charge the system. Measure the system pressure at any time by closing the can valve. Refer to the pressure gauge chart for refrigerant level and stop charging when you reach proper pressure.
	4. Attach Label: Confirm proper pressure, disconnect charging hose, reattach blue dust cap and attach retrofit label

Refrigerants

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Regardless of the type, all air conditioning systems function according to a basic law of physics that states ‘a fluid absorbs heat as it changes from a liquid to a gas, and a vapor releases heat as it changes from a gas to a liquid.’ In an A/C system, refrigerant is the transfer medium used to absorb the heat inside the passenger compartment and release it to the outside air. Refrigerant is a tasteless, odorless gas with an ability to change state rapidly within a specific temperature range. It is also oil soluble and non-corrosive. While there are scores of refrigerants on the market, there are only two types approved by vehicle manufacturers: R-12 and R-134a.

R-12, commonly referred to as Freon, has long been used as the refrigerant in all automotive A/C systems. However, R-12 contains chlorine, which is the primary cause of ozone layer damage. Consequently, legislation was passed calling for a halt in R-12 production by 1996. Long before the phase-out of R-12 began however, the automotive industry conducted extensive research and development to find an environmentally friendly alternative. They ultimately selected R-134a as the new refrigerant, and began using it in vehicles as early as 1992.

R-134a is similar to R-12, in that it absorbs, transfers, and releases heat efficiently. It is also non-flammable, and mixes well with oil, just like R-12. However, R-134a does have some unique characteristics.

R-134a requires a special synthetic lubricant since it does not mix with mineral oil (standard R-12 lubricant).
R-134a operates at higher discharge pressures than R-12. Therefore, systems using R-134a may not cool as well as R-12 when the vehicle is idling for extended periods (e.g. heavy traffic).
R-134a and R-12 cannot be mixed, which is why separate equipment is needed to service vehicles using either refrigerant.

Depending on the vehicle, refrigerant capacity can range anywhere from about 28 ounces (1.75 lbs.) to as much as 64 ounces (4.00 lbs.) or more. To avoid an improper charge, always consult the manufacturer's specifications for refrigerant capacity. An improper charge will cause reduced system performance, and may even result in system damage.

Refrigerant Oil

In order to function properly, an A/C system requires the appropriate type and amount of oil. In addition to lubricating the compressor, refrigerant oil also maintains the operation of the expansion valve on systems so equipped. Since the oil is transported through the system by the refrigerant, it has to be compatible with the type of refrigerant being used. Mineral oil is the lubricant used for all R-12 systems, while R-134a systems use synthetic oils such as PAG (polyalkylene glycol) and POE (polyolester).

A/C Recharging Method

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Push-Button Dispensing

With Measure & Charge (MAC-134) and EZ Charge (SD-134), dispensing refrigerant is as simple as pressing a button. You just connect the hose to the low-pressure port, press the button on the can to fill (to "charge") and release to stop. With Measure & Charge, releasing the button will automatically give you a pressure measurement on the in-line gauge (which is re-usable). Both let you store unused refrigerant for later. Both contain the appropriate proportions of refrigerant and oil, as well as System-Safe leak sealer. See full instructions on this site or on the can.

Trigger Dispensing

With the Quick Charge charging gun (QC-1CS and QCK-2CS), you simply connect the hose to the low-pressure port, screw a can of refrigerant into the Quick Charge, squeeze the trigger to dispense and release to stop. Quick Charge will automatically give you a pressure reading on the built-in gauge. Quick Charge is completely re-usable. See full instructions on this site or on the package.

Direct Charge Dispensing

With High Mileage Top-Off (HMT-1DC), you simply press the direct charge fitting onto the low-pressure port to fill 6oz. of refrigerant & oil (in the proper proportion). Great when all you need is a small amount of refrigerant to top off your system. We recommend using our EZ Gauge (GEZ-1) to measure pressure before and after charging to ensure proper pressure for peak cooling. See full instructions on this site or on the can.

Screw-in Can Tap Dispensing

Several of our recharging kits use the traditional method of dispensing, tapping a can. These kits are models RKR-7, RKR-5, RGM-134, GBM-134, and MB-134. This method involves screwing a can tap with hose onto a can of refrigerant, partly unscrewing to dispense, and screwing in again to stop. With the RKR-7, RGM-134 and GBM-134, you can check pressure with the in-line gauge. The RKR-7 and RKR-5 can be used in two ways: to either retrofit (convert) an A/C system using R-12 refrigerant to a system that can use R-134a refrigerant, or to recharge a system that already uses R-134a. See full instructions on this site or on the package.