AC Compressor Pulley Noise: Types, Causes, And How To Get Rid Of It

When the automobile AC is switched on, it releases refreshing and cool air, creating a relish and easy run for your driving.

The AC will draw in the humidity and heat from the cabin, which is transferred and undergoes multiple phases to convert into fresh and cold air.

If any parts run incorrectly in this process, you will find some AC compressor pulley noises. It’s not easy to drive a long run with some weird sounds.

To address the issue as soon as possible, you need to care more about what kinds of noises and where their key roots are to reach the right way to fix that.

Dive in with us now to get the details about the car AC compressor noise when engaged.

What Are Some Kinds Of AC Compressor Clutch Noise?

ac compressor pulley noise
AC Compressor Clutch Noise

What does a bad AC clutch sound like? There are nine types of AC clutch noise.

In particular, we can mention screeching noise, hissing sound, buzzing noise, knocking sound, rattling noise, growling noise, banging sound, squealing sound, and grinding noises.

Among those, we would like to emphasize the two most common sorts which a lot of drivers met and shared: rattling noise and squealing noise.

Rattling sound stems from weak compressor mountings. A worn or loose clutch hub also would trigger this kind of noise.

If there is something wrong with the pump pulley or catalytic converter, you can also spot this off-putting noise.

A screeching sound is super irritating due to its high-pitched nature, which can come from a worn air-conditioner compressor belt or a non-lubricated blower motor.

The sound is getting progressively worse, especially while throttling the vehicle.

Thus, in order to fix this problem, you need to get knowledge of the AC compressor in car making noise more clearly.

This will help you know what symptoms are on your vehicle and apply the right solution to repair that quickly.

What Causes AC Compressor Pulley Noise?

noisy ac compressor clutch
Why Is AC Compressor Pulley Noise

A strange noise from the AC compressor pulley might hint at a failure in the pulley, compressor clutch, serpentine belt, a broken compressor, worn-out bearings, or miscellaneous problems.

Whatever the reason, it’s best to inspect each component whenever you detect an abnormal sound.

Compressor Clutch

The car’s compressor clutch is one of the easy-to-rust parts. Once it wears off, it will generate some rattling sound during the run.

Some cars just require you to change the defective clutch, while others might call for repairing or replacing both the compressor and the clutch.

This part is the key root for the loud AC compressor car when it’s not operating.

Miscellaneous Problem

There is a wide range of culprits to blame for the sound. When the car’s AC switches on, this means that its entire engine is put under a heavy load.

This hefty load might trigger some sounds, especially rattles, from some elements like loose components (even a hood prop rod (flexible one) can create a noise under the extra vibrations made by running the air conditioner) and the steering pump pulley. 

Bearing Wear

Once the bearing has got a problem, some sounds might stem from the vehicle’s idler pulley. The AC bearing noise will start as the compressor runs because of the heavy load on the car’s engine.

Poor Serpentine Belt

In case your car’s serpentine belt is worn down, it is not hard for it to slip during the engagement of its compressor.

As such, it will lack the friction needed for the belt to run smoothly and noise-free.

This is a breeding ground for a noisy AC compressor clutch. In addition, a torn serpentine belt can even make the situation worse (louder noise) than ever.

When installing a new one, remember to tighten the serpentine belt properly.

Bad Pulley

If the AC compressor pulley is out of order, it might make some sounds, especially a squealing, roaring, or grinding noise.

The sound can be indeed louder from the compressor pulley if the bearings are in bad shape.

Then, the part begins to generate sound under the heavy motor loads. Even when it does not engage, a swaying pulley would be the main cause of the AC clutch sound.

Broken Compressor

Once the AC compressor starts to show signs of damage, it will probably produce a rattling sound.

Not to mention, if your car receives some rough handling due to its badly-maintained system, compressor failure will happen more frequently.

The compressor failures sometimes make the AC compressor shut off right after a few seconds. So you should check this part soon once you detect any weird sound before it’s too late.

How To Fix AC Clutch Making Noise 

ac compressor clutch noise
Repair To AC Clutch Making Noise 


If you do not have much experience in the field, you should ask for help from skillful mechanics when you hear a rattling noise from your car.

Nevertheless, the below tips might give you some help to correct the problem: 

  • Change the AC compressor clutch or belt, and ask a mechanic to have an inspection on the AC system, which aims to determine the actual issue.
  • Ensure the fans and hose belts are in their proper places without any unexpected effect on the compressor.
  • The mixture of lubricants or the specified lubricant for the compressor clutch is recommended in this case. For oil mix, the mixture proportion needs to meet the specified ratio. This will align with the balance of these oils (which you can check on the product instructions).

Don’t forget to replace the fuel when due. Add more lubricant via the nominated port on the AC compressor, ensuring the right volume.

Introduce some drops of the oil to the cylinder to grease the clutch. Buy lubricants from certified or reliable dealers.

  • Change the clutch if any of the resorts mentioned above can not fix this sound.


A slapping or knocking sound in the car air-conditioner compressor clutch could be a trivial sound to fix without the help of an expert.

  • Observe the wobble parts of the compressor clutch, then screw the nuts up. In addition, apply thread-locking matter on the loose components to prevent them getting loose easily.
  • Have an inspection of the cooling parts and check whether there is a certain issue with the mounting bolts. In case these apparatus are indeed in trouble, the movement of these nuts will show the condition of losing.

You should utilize a spanner to tighten the loose nuts and bolts. If you don’t want the problem to recur, let’s buy a thread-locking substance.


  • First of all, have a look at the user instructions and use the manual. Step by step, check the cooling system to see if it has any leakages. Once you find any leak, take the Freon set from the repair kit (if any) and use it following the manual.
  • When the noise is on the rise and becoming worse, consulting a skillful mechanic to repair the AC is necessary.


  • Exam the fan belt to know whether there is any looseness or cut.
  • Check the car’s hoses to find any signs of damage.
  • Clean the automobile AC belt if it’s dirty.
  • Ask a professional to fix the issue if your tries yield nothing good.

Screeching Noise

  • Spray water on the car’s AC belt to lessen the noise. 
  • Change the AC belt: after you use water on that and see nothing is better, check the part to find any potential damages; if the finding is negative, it is the right time for you to get a new AC belt.
  • Having a general inspection on the entire car to determine whether it has any weird issues.
  • Screeching stemming from the vehicle AC clutch is quite harmful to the apparatus and needs to be repaired as soon as possible. Thus, it would help if you still asked an experienced specialist to verify the issue correctly.

Yet, inspecting the serpentine belt is within your reach.

You need to have more consideration on some worn-out indicators like rips, or cracks and missing ribs which face the automobile pulley before driving it to the garage for servicing.

Banging Noise

When it comes to the kind of sound created by your car’s engine, the most common and safest approach is to ask a pro for some help

Grinding Noise

It’s similar to the banging sound, and you need to ask a skillful technician to get the best resort to address this issue.

Final Thoughts 

We walked through the hot content of the AC compressor pulley noise together.

Until these last words, you’ve established a level of understanding of AC pulley noise types, their causes, and solutions to fix that properly.

It would be best if you put more consideration on rattling, knocking, and screeching noises, which are prevalent sounds most drivers usually encounter when driving.

Also, you should pay more attention to frequently checking and maintaining your car to find some potential issues as soon as possible.

It is the right time to put an end to the post today. Thank you for your company, and see you soon in our future blogs.

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