Squealing Noise When AC is Turned On (Here is Why)

Have you ever heard unusual sounds as you start your car? When you notice shrieking sounds whenever you start on the car air conditioner, it indicates that your compressors or belt is malfunctioning.

Screeching sounds are an added disadvantage. This article will explain it in more detail.

The Common Reason for Squealing Noise of AC

Squealing Noise When AC is Turned On

The usual reason your car AC makes a high-pitched noise is a malfunctioning AC compressor clutch.

The AC compressor clutch is critical to your vehicle’s air conditioning system. If the compressor clutch is defective, your air conditioner will not blow cold air and create a squealing noise.

This component is responsible for pressuring the entire air conditioning system and pushing the refrigerated air through the cooling system. The ac compressor clutch cycles on and off due to these two critical functions, and it eventually wear down and breaks.

Reasons for Car AC Compressor Clutch Failure

The AC compressor clutch might fail for various reasons, which are as follows.

Low-Cost AC Refrigerant

The clutch may not engage or create screeching noises because it has low amounts of AC refrigerant. Sensors in the air conditioning system check to see if the system has appropriate pressure. The AC clutch does not undertake if there is a stress problem.

Worn Out Components

Bearings, brackets, and tensioners are part of the AC compressor clutch. Most of us drive with the air conditioner on practically all the time, putting a strain on the AC clutch.

These components will wear down over time, and the AC compressor clutch will fail. Dust, grease, and moisture also build up over time.

Improperly Installed Parts

When an AC professional makes a mistake, they may install some minor parts incorrectly.

A poorly fit bearing will not immediately exhibit any signs of failure, but it will eventually fail. Human mistakes occur in every sector, and we can do little to prevent them.

Weak AC Compressor Pulley and Bearing

When the engine runs, the AC compressor pulley links to a drive belt and rotates at all times. While turning, a defective ac compressor pulley and bearing might generate screeching noises. Although the AC compressor pulley spins, the shaft does not.

When the air conditioner switches on, the compressor shaft revolves. Since it rotates as the engine starts, this component can wear down over time and make screaming noises.

Why Is My Car A/C Making Noise When I Turn It On? Check Video

Why Compressor Bearings and Pulleys Fail?

Here are a few of the most common causes of ac compressor pulley and bearing failure.

Excessive Heat

It is the number one enemy of all automotive air conditioning components. Extreme heat produces while the AC compressor pulley rotates with the bearing, causing damage to the pulley and bearing seal.

The revolution creates heat that can exceed 1200 degrees Fahrenheit. This heat will dry out the grease in the bearing, resulting in a squealing noise.

Compressor Shaft Seal Leakage

When the compressor shaft seal leaks, it goes into the bearing grease and contaminates it. Bearing grease and shaft seal grease have different characteristics. Thus, the grease inside the bearing would be unable to lubricate it.

Refrigerant Leaks

Suppose the AC refrigerant lines break. It causes refrigerant leaks. In this condition, the compressor will not work.

Also Read: Humming Noise in Car Getting Louder with Speed (Here is why)

AC Belt is Broken

The AC belt links the AC compressor clutch to the engine crankshaft when you activate your car, allowing the AC compressor clutch to rotate. A broken or worn-out AC belt will make screaming noises when you turn on the air conditioner.

There are two kinds of car Ac belts, V-Belt and Serpentine belts. The form of the two is what distinguishes them. You can change your car AC belts if you hear squealing noises.

How to Solve the Problem of AC Squealing Noises?

How to Solve the Problem of AC Squealing Noises

The air conditioning system depends on the pulley and bearing of the AC compressor. Here is how to replace an AC compressor pulley and to bear if they are affected.

Remove or Change the Pulley and Bearing

The compressor is behind the engine bay. By removing the passenger side wheel, you can access it from the top or side. To remove the compressor clutch, you will need a 6mm socket. Remove it when disconnected.

Rotate the Pulley

Rotate the pulley to see if it works. If the compressor pulley does not turn on, the problem is with the compressor. Using a hammer or two-point hammer, remove the compressor pulley. The compressor pulley has a bearing inside it. If the bearing is safe, you will need to replace the entire compressor pulley with a new one

Replace the Bearing

You can replace a bearing if it is faulty. You’ll need a socket and a hammer to remove it. Once you replace it after installation, test the pulley to see if you fixed it.

Fix or Replace the Broken Belt

The AC belt should be one of the first things you check. It is present over the compressor. If the belt appears weak or worn out, you need a new one.

You should be able to remove the belt with your bare hands after loosening the AC belt tensioner. Ensure the pulleys are clean and free of any rubber from the belt. Tighten the AC belt tensioner after installing the replacement belt.

Check Your AC Belt Type

As previously stated, the AC belt can be either a v-belt or a serpentine belt. Their size is what separates them. With only one rib, the v belt is slimmer. 

There are multiple ribs in the serpentine belt. With a wrench, unscrew the bolt on the AC belt tensioner. Depending on the car, the AC belt tensioner can loosen by rotating clockwise or counterclockwise.

Repair the Compressor Clutch

It would be best if you disconnected a connector on the magnetic coil of the compressor. The AC clutch should have a 6mm socket in the center that you will need to remove. Disconnect the clutch and pull it out.

Make sure the spacers on the shaft don’t get lost because they gap the clutch, and you’ll need them later. You will see a snap ring on the shaft. Remove and slide it off. Clean all parts, then start the installation.

Here is an informative video on repairing your AC Clutch and diagnosing noise.


A malfunctioning AC unit compressor or a damaged belt would not affect the engine’s general performance, but it will prevent cold air from entering the cabin. Fixing it will ensure your comfort and safety.

Leave a Comment