Mercedes Benz Air Conditioning Compressor

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 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

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:

  1. 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.
  2. 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.
  3. 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.
  4. If the line that leads from the receiver/drier to the condenser is a lot colder than the other line, the system is undercharged.
  5. 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:

  1. 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.
  2. 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.
  3. 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.
  4. 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

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

R134A Machine

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.