When you want to cool down on a hot summer day, it's as easy as pressing a few buttons on your car's dash, unless something isn't working properly. If the air conditioning system is not functioning correctly, you could be looking at a faulty or failing compressor. This part is responsible for pumping the refrigerant through the a/c system, which in turn chills the air coming through the vents and offering relief from the heat to you and your passengers.
Since it has such a hefty job, the compressor has to work very hard to meet demand and as such it gets very hot. There are a number of reasons the compressor can fail, but the most common is a lubricant leak. The mechanism operates in a delicate balance, relying on a small amount of lubrication to keep its parts moving fluidly. If a leak forms, the motor will be unable to run well, if at all. This often results in a compressor seize, which is sometimes evidenced by a squealing sound coming from the drive belt. In turn, a seized compressor could damage or break the belt and pulleys. So if the a/c is not working, try to leave it off unless you're troubleshooting the part to avoid damaging other engine components.
If you are unsure whether the compressor is the reason the a/c isn't working, you can check by starting the car, turning on the a/c and popping the hood. Locate the compressor, which is a pump with two large rubber-and-steel tubes coming out of it. The part should have a pulley in front and another one inside that turns when the car is idling. If you don't detect motion, but hear the fan blowing, then the compressor is not functioning.
Before you even consider a serious problem, check the fuse first. The fuse panel for engine components is located under the hood in most vehicles, so consult the owner's manual if you are unsure where to find it. This will also help you determine which fuse correlates to the compressor.
After you've checked the compressor for lubricant leaks and inspected the fuse, the next part to investigate is the magnetic clutch. If this part is not engaging when the a/c is on, you could be looking at faulty wiring, a blown fuse, problems with the relay or a faulty control module. The clutch may also have a low-pressure cutoff switch, which disables the part if there is not enough system pressure, or refrigerant charge.
The air conditioning compressor may also just be nearing the end of its useful life. Compressors are built to last at least a few years, and factory installed parts will typically have a longer life expectancy than aftermarket compressors. However, you can extend the life of your car's compressor by being vigilant about its care. If your car does not use the compressor for the heating system as well, as many models do, you should make sure to crank the air conditioner for a few minutes every couple of weeks all year long.
When you discover a problem with your air conditioner, it is best to leave the repairs to a certified expert. The refrigerant contained within the system consists of materials that are damaging to the environment and must be handled and disposed of properly.