5 Bad Car Air Conditioner (AC) Noises and How to Fix Them!

If your car’s air conditioner is making a noise, that’s something you should look into right away. The last thing you want is a broken car air conditioner when summer rolls around. That’s why today we will help you identify the different kinds of bad car air conditioner noise!

Whenever your car AC is making noise, it means there’s something wrong. So, whether your car AC makes a noise when turned on or turned off, it’s best to check it out. That way, you can determine what it means and take action. If you want to learn how to quiet a noisy car AC compressor, continue reading. 

5 Bad Car Air Conditioner (AC) Noises and How to Fix Them

Squealing Bad Car AC Sound

If your car air conditioner is making a squealing or screeching noise, the serpentine belt could be the issue. The serpentine belt is what turns the pulley in the AC compressor and that’s what pressurizes the refrigerant lines. That way, cool air can fill your car. 

So, if you’re hearing a squealing sound, check the serpentine belt for signs of wear and tear. Look for tears, cracks, or missing ribs. If it’s too damaged, you will need to replace it to eliminate the noise. 

You must get a mechanic to fully diagnose the issue before you do anything. However, you will likely need to have your serpentine belt replaced. This guide on how to change a serpentine belt will help you understand the process. 

Knocking or Clicking Bar Car AC Noise

When your car air conditioner is making a constant knocking or clicking sound, you need to check the system for loose bolts or components. If you run the engine and open the hood, you might be able to see where the noise is coming from. 

Just stand back and keep an eye out for areas that seem to be shaking, because that means something is loose. The easiest solution for this is to tighten the loose bolts or components, which is something you could do yourself. 

You can also go the extra mile and use a thread-locking compound to keep the bolts in place for longer. This is probably the easiest bad car AC noise to deal with!

Buzzing Bad Car AC Sound

If your car’s air conditioner is making a buzzing noise when you use it, you might want to check the compressor. A buzzing sound is one of the most common signs of a car AC compressor going bad. Usually, it means the system is overcharged with refrigerant. 

When there’s too much refrigerant liquid in the system, it will enter the compressor intake port and lead to vibrations. That’s not good at all because it can compromise the lifespan of the compressor. Compressors are expensive to replace, so it’s something you must take care of.

As soon as you hear your car AC making this noise, check to see if there’s excess refrigerant so you can remove it. You want to do this ASAP. Otherwise, the AC won’t cool properly and the components will get damaged. This short guide on how to remove excess refrigerant is helpful, so check it out!

Rattling Bad Car AC Noise

If your car AC is making noise and it’s a kind of rattling sound when you turn it on, it could be due to different things. For one, it could mean the compressor is going bad. It could also mean the serpentine belt or idler pulley are wearing out. To determine that, get it checked by a professional. Additionally, there’s a chance that the compressor clutch is wearing down. 

The compressor clutch needs to be replaced more often than we’d like compared to other parts in the AC system. So, if you hear a rattling noise, make sure to inspect the system to see if there’s something wrong. Better yet, take it to a professional to get it diagnosed. 

If the AC compressor is the issue, you’ll also hear a humming noise that will intensify when you accelerate. Both the rattling and humming often mean that the compressor needs to be replaced. To be sure, get it diagnosed by a professional or refer to the last section of this article for more info. 

Hissing Bad Car AC Sound

If your car’s air conditioner is making a hissing noise, it’s more common than you think. If you hear this sound when you turn the vehicle off, it’s due to pressure equalization. 

That happens when the refrigerant moves from the high-pressure side to the low-pressure side of the compressor. This is a completely normal sound and it doesn’t mean anything’s wrong. 

However, if you hear the hissing sound at any other time, you should get your AC system checked by a professional. This way, you’ll know if there’s anything wrong and solve the problem quickly. 

In case you’re experiencing lifter tick noisealternator noisebad wheel bearing sounddifferential whine noisecatalytic converter noisecar clunking noise, car clicking noise we have got that covered too.

How to Diagnose a Bad Car Air Conditioner (AC) Compressor

The compressor is the beating heart of any air conditioning system. It is a pump that creates heat by exposing the refrigerant to extremely high pressure. It’s called a pump because it can increase the pressure on the refrigerant and also transport it through the pipe. 

If you suspect there’s an issue with your car AC compressor, here are the signs to watch out for: 

Unusually High Temperatures

One of the most common signs of a bad AC compressor is unusually high temperatures. When your AC is no longer blowing cold air, the compressor is either damaged or failing. 

If the temperature rises inside of your car when you’re using the AC, you should check if there’s enough refrigerant. Also, make sure there aren’t any refrigerant leaks. If everything’s okay with the refrigerant, you’ll need to check the compressor. 

Loud Noise

It’s normal for your car’s air conditioner system to make noises when you turn it on and off. However, if the noise is very loud and it continues while you’re using the AC, you might need to check the compressor.

This is another obvious sign there could be something wrong with the compressor. Maybe something’s broken or failing inside the compressor. The best thing you can do is go to a professional to determine the issue. 

Refrigerant Leaks

If the AC compressor has moisture leaks, it means it needs your attention right away. The refrigerant is essential to the AC system because it helps turn warm air into cool air. 

When the AC compressor doesn’t have enough refrigerant to work with, it will produce only warm air. So, if you feel warm air coming out of the AC, it could mean the compressor is leaking refrigerant. This guide will show you how to find leaks.

Damaged Compressor Clutch

The compressor clutch allows the pulley to engage and disengage as necessary. That way, the compressor only works when it needs to. So, when the clutch breaks, the compressor won’t be able to receive engine power. 

The good news is that replacing the compressor clutch is much less expensive than replacing the compressor entirely. So, take your car to a professional to get it diagnosed. 

Faulty Circuit Breaker

If the outside condensing unit of your car loses power constantly or the circuit breaker is tripping, it means the compressor is going bad. When the compressor is not working as it should, it would overheat and draw too much power. That will lead the circuit breaker to constantly trip. 

The last thing you want to do is reset the circuit breaker constantly to be able to use the AC. Why? Because it’s protecting you from a potential fire hazard. So, if it’s tripping, stop using the AC and take the car to a mechanic. 

Damaged Refrigerant Lines

If the AC compressor fails, the refrigerant line to the AC will become blocked. That will lead to hot airflow inside the car, which is a big issue. A mechanic will unblock the refrigerant lines successfully. If they can’t, then it means the lines must be replaced. 

This guide can give you an idea of how to replace an AC line. This is just so you know what the process entails. If you don’t have mechanic experience, we recommend you leave this job to professionals. Some things are best to not DIY. 

Damaged Wiring

Last but not least, damaged wiring is a big sign of a bad car AC compressor. If you keep up with car maintenance, you will notice damaged wiring very easily. Once you do, you need to handle it right away. 

Damaged wires increase the risk of electrical fires, so you shouldn’t wait too long to get them fixed. When your car AC unit is exposed to electrical issues, the compressor may receive too little or too much voltage. That will only damage it quicker!


If your car’s air conditioner is making noise, it won’t be as difficult to solve as you may think. Granted, if the issue is the compressor, you may be facing an expensive repair. However, that’s not always the case! Use this guide to diagnose your AC and take action ASAP. 

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