For many of us, as long as our
car is running well, we may not think about the hundreds of parts
working together under the hood to bring us our creature comforts. The
air conditioning compressor is one of those parts that typically gets a
lot of usage and provides that critical cool air on hot summer days. The
air-conditioning compressor does exactly what its name says -- it
compresses refrigerant and sends it to your car's air condenser. The
entire process is powered by your engine's drive belt (or belts). The
highly pressurized liquid refrigerant converts to a gas and is
circulated into tubes where the heat from the gas is quickly released,
causing it to cool. The cooled gas then reverts back into liquid form as
it returns to the compressor. The cooled gas is used to chill the car's
cabin air.
As with any other part on a car, it's difficult to
determine exactly how long any one specific component will ultimately
last, but there are some factors that help determine how long a
compressor will be able to do its job. The first is the age of the car.
Most modern cars have air-conditioning systems that are considered
reliable, so major issues are rare. But similar to other car parts, as a
car's age and mileage begin to add up, you can expect that the wear and
tear over the years will cause parts to fail or malfunction. In the
case of the A/C compressor, this can mean little or no cool air coming
from the system.To keep your car's compressor in shape throughout the year, it's recommended that you run the A/C compressor regularly, to keep the system working properly and to extend its longevity. Many cars use the A/C compressor for functions of heating and ventilation in the defrost cycle, too. But if your car doesn't, you should run the compressor for at least 10 minutes each month, even during the winter months.
One last point to note: If the compressor has already been replaced in your vehicle, the lifecycle may not be quite as long as the factory original part. Many aftermarket auto parts websites will quote a one- or two-year warranty on the part -- but, of course, they can certainly last much longer with the proper care.
So, if you notice that your car's air conditioning system isn't putting out any cold air, or minimal cold air, a dysfunctional or broken compressor could be the culprit (among several other possibilities). Just remember that compressors function at high pressures, involve liquid refrigerant and require special tools to service -- it may be best to leave changing the compressor to an expert mechanic.
Source: howstuffworks.com