When it comes to troubleshooting car problems, unusual sounds from under the hood can be among the hardest ones to isolate. The good news is, though, that there are some things you can do to determine the source of the noise and address the repair. One common cause of unusual noises from your car's engine is an AC compressor pulley that's binding up or failing. Here's a look at what you need to know about identifying and dealing with this issue.

Signs Of A Failing AC Compressor Pulley

It's important to recognize the signs of an AC compressor pulley that's failing to protect your car's serpentine belt from potential damage. Unlike when the compressor itself is failing, you won't necessarily notice signs of a failing pulley when you run the air conditioning. 

Instead, the pulley will exhibit signs that are most easily heard from outside the car. If your car is idling and you hear a grinding or whining sound coming from the engine, it's a good indication that one of your pulleys is going bad. Figuring out which one usually requires that you pull the belt off.

Checking The AC Compressor Pulley

If you have reason to suspect that the AC compressor pulley is the problem, the first thing you need to do is locate the AC compressor and pulley in the engine. The serpentine belt will route around that pulley, but it also runs around the idler, tensioner, power steering, and water pump in most engines. That means going through the serpentine belt path to identify which one is the air conditioning compressor pulley.

Once you have removed the serpentine belt, you can check the air conditioning compressor pulley by spinning it by hand. Without the tension on the pulley from the belt, it should spin. If you can hear any kind of grinding, squeaking, or other noises from the pulley, that's an indication of a problem with the pulley.

If you feel resistance in the pulley when it spins, that's also a key indication that the bearing in the pulley may be binding up. Most AC compressors are now complete units, so you can't simply replace the bearing or the pulley itself. However, some models do still have a removable pulley that allows you to replace just the pulley.

Preventing Complete Pulley Failure

Once you've confirmed that the AC compressor pulley is failing, you'll have to replace either the pulley or the entire compressor, depending on the assembly. The longer you wait to replace the pulley, the greater the chance that the pulley will fail completely. If it seizes up, it could potentially damage the belt, causing the belt to shred.

You can avoid this risk until the repair by investing in a shorter serpentine belt. Then, route the belt so that it bypasses the AC compressor pulley. Then, you should be able to run your engine without the noise or the risk of the compressor failing.

Once your car is safe to drive, you can reach out to your local car repair center to schedule the compressor pulley replacement. Look for a shop like Huntington Beach Transmissions if your car is making a noise.