AC Compressor Failure [10 Things To Check & Solution Guides]

Your AC compressor can fail when it has low freon levels, a stuck valve, or if the compressor clutch is not working anymore. When your car air conditioner starts to act strange there could be a number of reasons why, but one common reason is the compressor.

Common areas to check to see if your AC compressor has failed or not:

Check if the air temperature is warmer than normal. Usually, the first indication of a problem. Starting the car and pressing the peddle to 2000-3000 RPMs while the car is in Park. Feel if the air gets colder and colder as you continue to press the peddle at 2000-3000 RPMs. This likely means the AC compressor isn’t working as it should.
Check if you smell something? According to some, you can smell a sweet smell if you have a freon leak. Be sure to check for an antifreeze leak, because both smell sweet.
Listen for noises that occur when the AC is on. This could be a mechanical problem with the compressor.
Check if the AC temperature is too warm or too cold from what is normal or it alternates between both. This could be a clogged or bad AC expansion valve. If you notice the AC compressor is always on, this could also mean an expansion valve issue or a damaged compressor clutch.
Turn off the car and check under the hood for loose or damaged wire connections to the compressor. A loose or damaged wire could cause a short or sporadic compressor activity.
Check the fuse box for blown fuses. Bad wiring or a bad compressor could cause a blown fuse.
Check the compressor clutch – See video – Supply 12V power to the compressor clutch wire. If you hear and see the clutch engaging, the clutch is likely fine; if not, the clutch could be the problem.
Check freon levels – Check the sight glass in the receiver dryer or other areas of the AC system or use a manifold gauge. If it has lots of bubbles or little liquid flowing through it when AC is on, the freon is low. This can cause the clutch to freeze.
Check for a freon leak. If you suspect a leak you can turn the AC on, wait a couple of minutes for pressure to build, turn off the car and check the entire AC system using an electronic detector, or by spraying a soap and water solution on all areas needed and looking for bubbles. An easier method might be using a dye that you add to the AC system and using a black light to check where the leak is occurring.
Check the cooling fans. If the cooling fans on the “condenser or radiator” are not turning on when the AC is on, this could be the problem.

Your compressor could be bad, but it could be a number of other issues as shown in the article below. Use the troubleshooting guides and with a little luck, you can find the problem without a big expense at the mechanic. (Use caution whenever working on your AC system and avoid turning the AC on if possible to avoid AC compressor damage.)

First Steps To Diagnose A Bad AC Compressor

There are different AC systems that work a little differently for different cars, but the compressor clutch is basically the same for each car.

To start with you can do some quick checks to narrow down the problem. I would start with what I know already and check those areas or parts. If your check reveals trouble, plan to spend more time focused on that area to see if you can solve the problem.

Some parts to check first are the compressor/clutch, the serpentine belt, and the refrigerant. These are usually the first to go bad.

An older car will likely have worn-out parts, while a newer car can have malfunctioning parts.

For older cars, you may want to start by:

Listen for odd sounds from the compressor. If very noticeable, then it’s likely bad.
Look at the clutch when the AC is on. “If the clutch is engaging and disengaging once every few seconds, this is a sign of low refrigerant.” (autozone.com)
If you are not sure the clutch is working, you can test the compressor clutch with a circuit probe tester (Amazon Link) (See video below).
Check freon levels – Bubbles or no liquid flow in the sight glass means freon needs to be added.
Check the wiring. Look for loose connections and frayed areas.
Check to see if power is getting to your compressor using a multimeter.
Check the fuse box for a blown fuse.
Check for freon leaks.
Check the serpentine belt is not slipping or worn. (May hear a screeching noise.)

An older compressor clutch has seen a lot of use. It may go bad from lots of use, or a slow leak in your AC system. Low freon can cause excessive wear to your compressor, like an engine without oil. (See article – How Much Oil Should You Add Up In AC compressor?)

In addition, the wiring in your older car can become loose, damaged, replaced with the wrong type, or corroded. Wiring is another big issue with older compressors. Testing wiring and checking fuses will let you know if the wiring of the compressor is likely the problem.

Last, you want to check the entire AC system because the could be problems with other components or a leak in the system somewhere. This is where you will need a lot more time and patience. Sometimes this is the step when you need to go to a mechanic because it may take more time and expertise.

For a newer car, you may want to start with:

Newer cars are more likely to have a freon leak or loose wiring rather than a worn-out compressor.
Look at the clutch when the AC is on. If you see the clutch engaging and disengaging frequently, this could mean there’s not enough freon in the AC system. Your compressor is likely OK, but freon should be added to avoid damage to the compressor.
If you’ve had your car worked on recently or done some type of engine service, you should check the wiring and see if power is getting to your compressor using a multimeter or circuit probe tester (Amazon Link). I’ve noticed that mechanics or service technicians from time to time forget something when they are in a rush.
Check the fuse box for blown fuses.
Check for freon leaks. Use the sight glass if your car has one to see if levels are good as described earlier. If no sight glass, you can try a manifold gauge set (Amazon Link) to test pressure and even add refrigerant.

Newer cars will have more electrical problems before mechanical problems unless there’s a leak that is likely caused by damage or someone who worked on the engine or AC system. I would focus on seeing if power is getting to the AC compressor clutch and fuses that might be blown.

(Cost to buy an AC compressor generally ranges from $150 – $300. Labor can cost about $500 – $1500 for the average car. If you are sure the AC compressor is the problem, you replacing it for cheap enough. Although doing it yourself can be fairly difficult for the beginner.)