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Air Conditioning Compressor

What is an Air Conditioning compressor?

Your car’s air conditioning uses a special refrigerant that’s gaseous at room temperature and pressure. This refrigerant is compressed to over 200 psi, which heats it up. The refrigerant is then passed through a condenser to shed much of this heat. It then passes into the evaporator inside your cabin, where its pressure is rapidly dropped, soaking up the heat in your interior. This cycle continues constantly. The compressor is driven by a belt from your engine.

What are the symptoms of a failed compressor?

A compressor can develop a leak, venting refrigerant to the atmosphere. This will make you’re A/C blow warmer and warmer air, until it eventually ceases to keep up. Unfortunately, other things like hoses and condensers can leak, so a technician will need to identify where the leak may be stemming from. A more catastrophic failure is caused by broken pieces inside the compressor (remember, it’s crammed full of moving parts, spinning at nearly the same rpms as your engine). Compressor failure will generally make the pulley stop spinning because it’s full of broken parts. This will cause the rubber belt to screech, smoke and melt within seconds. If this belt is in common with the other engine accessories (like the water pump and fan), the car will not be drivable. Some vehicles use a separate belt for the A/C, and simply removing the belt will let you continue on your way to the repair shop.

What is the severity of a failed compressor?

A leaky compressor will need to be replaced. Period. Additionally, the system will need to be purged, and then evacuated and refilled. This should also include careful leak testing before and after to be sure it’s only the compressor that’s the culprit.

Obviously, a compressor that has destroyed itself internally will need to be replaced. That means using an expensive recycling machine to suck the refrigerant out of the system, because it’s illegal to vent it to the environment. Worse yet, the swarf (broken pieces of vanes, pistons or other internal parts) from the compressor have now contaminated the rest of the system, requiring careful flushing to remove. Standard practice is to replace a component called the receiver/dryer, because it has several internal filters that have probably become clogged with detritus as well. Then the system has to be evacuated to remove all air and moisture, and then recharged with a carefully-measured amount of the correct refrigerant. This is all time-consuming and requires specialized equipment and trained automotive technicians.

What’s the cost to replace a compressor?

A simple compressor swap will cost $200-600 for the compressor and refrigerant, plus another $200-300 for labor. Flushing a contaminated system and replacing the receiver/dryer could add another $100-200 to that bill.

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Article written by ASE Certified Mechanic