AC Compressor Noise At Idle: Reasons And How To Fix

AC compressor noise at idle is a frequent issue. A pulley is being impacted, or your AC clutch is broken.

You don’t have to visit a mechanic right away.

You need to know more about the type of ringing, such as a bell or squeal, and what your engine speed is at idle because you need to increase the revs from 750 to 1500 to turn on the air conditioning.

Find out more by reading the article.

What Is A Car AC Compressor?

ac compressor noise at idle
Car AC Compressor

An AC compressor is a small pump with a clutch on the front of it. It occasionally engages, pumping refrigerant into the expansion valve to create a cool ride.

It is driven by a drive belt attached to the engine’s crankshaft, which circulates the refrigerant through coils to efficiently remove heat from the car.

The gaseous refrigerant is pumped from low pressure to high pressure by the AC compressor through the refrigerant line.

The refrigerant is transferred from this hotter gas to the condensation in front of the radiator, which condenses to a cooler liquid condition before being pushed back to the cabin evaporator.

This liquid refrigerant cools the vehicle by absorbing heat from the cabin air as it is extended through the evaporator.

The right oils and refrigerant are essential, as is avoiding moisture that could freeze and clog the system.

Desiccant dryer modules are used in common procedures and must be replaced when maintained.

Also, once the system is opened, the leak must be rectified, and the system must be evacuated to get rid of any moisture.

What Types Of AC Compressor Noise At Idle?

There are numerous types of noise from car AC compressors. Each variety has a unique cause and remedy.

Whirring, rattling, whining, and other strange noises from your car’s air conditioner can point you the right way and help you avoid expensive repairs.

Whirring Noise

Whirring noises are made by the AC compressor from time to time when it is running normally.

Frequently, an AC at idle whirring sound may start to occur soon after the system has been maintained and filled off with refrigerant.

Nonetheless, every car owner must hear the whirring sound of the automobile’s air conditioning compressor.

A whirling sound may signal the device has been overloaded with refrigerant. It could result from performance problems and, worse yet, system component damage.

You may have a mechanical issue with your automobile if the AC compressor noise when the idle engine type sounds like a helicopter.

Whether your interior blower, outdoor unit, or fan is broken, your AC compressor makes a helicopter-like noise when running.

Rattling Noise

A common source of rattling sounds or humming noise in systems is an AC compressor failure or other components with loose or compromised mounting.

Sometimes the noise may come and disappear. Something is vibrating against the AC compressor in your car when this happens.

The compressor itself may make rattling or knocking noises. There are several reasons for this. For instance, a hose, fan, or belt may be to blame.

The car air conditioner noise might get louder as you go faster. It indicates that a malfunctioning part is causing the noise, and the compressor has to be examined.

The compressor is often replaced with a new or rebuilt one.

Whining Noise

Bearing failure results in whining noises. If you don’t have a bad bearing, you can have a serpentine belt that is wearing out.

Check the belt, please. It’s probably old enough to warrant replacement if it’s loose enough to screech.

You can see where that’s headed; a little slippage will glaze the belt’s surface and make it more slippery.

Moreover, when the belt is off, check to see if the tensioner’s bearings are in fine condition and replace them. The noise is a warning that the belt will fail sooner rather than later.

Squealing Noise

On the other side, blowers and fan sound at idle, causing squealing noise. These two make noises that sound like screeching sounds and are carried through the duct system.

It’s common for the air conditioner to make a low, screaming noise. The AC compressor clutch is what you hear engaging.

A worn clutch, however, can make a loud roaring sound. Hence, consider this to be a cautionary tale.

But, if you often hear quick squealing noises when the blower motor starts, an obstruction may prevent the engine from working properly.

Reasons For Ac Compressor Noise At Idle

car ac compressor making noise
What The Causes Of Ac Compressor Noise At Idle

The noise could come from a variety of places. The reasons you could hear the noise emanating from your car’s AC system are covered in detail in the following section.

Fail AC Compressor

When your car air conditioner noise when idling, the compressor is likely malfunctioning. Unlike refrigerant leaks, it indicates a mechanical shift somewhere in your car’s air conditioner.

AC compressor sound near the engine can be attributed to many offenders. The belt squeaks, the power steering pump whines, the pulley is worn out, and the brake pads must be replaced.

During the examination, you notice the AC compressor rattling, chirping, whining, chattering, or chattering noises.

One of the essential parts of an air conditioning system is the AC compressor. Repairing your AC compressor may be expensive.

Fail Pulley

The engine’s accessory drive system assists the AC pulley, also known as the air conditioning pulley, which ascends to the front of the air conditioning compressor.

When your automobile is at base idle, one of your pulleys needs to be changed if the engine grins or whines.

The AC pulley itself rarely has a problem, but the bearing it rides on frequently needs to be replaced. There will be externally audible indicators of a broken AC compressor pulley.

These issues typically have slightly varied root causes depending on the vehicle model.

Worn Serpentine Belt

When the compressor activates, a worn-out serpentine belt may slip. It will squeak if the belt is stretched out and worn.

Your car’s power steering, cooling fan, water pump, and air conditioning will all cease working if the serpentine belt snaps.

Your vehicle will run without an air conditioner and a radiator cooling system, and the engine will heat up quickly.

The AC compressor can damage the serpentine belt in a few different ways. The shock load may snap the serpentine belt if the AC compressors seize while in use.

It is always a good idea to replace the idler pulley and tensioner for the serpentine belt at the same time as the belt.

Fail Idler Pulley

Most frequently, a belt tensioner is connected to an idler pulley.

If the belt tensioner begins to malfunction, the belt won’t be held as firmly in place, and if it’s a cam belt, it may hop or skip teeth.

If it’s a regular alternator/AC belt, it may slip, wear down quickly, and eventually fail.

A bad tensioner can exhibit many of the same symptoms as a bad idler pulley bearing.

While the bearing and pulley work to maintain the belt properly aligned on the other drive pulleys, it may result in uneven belt wear.

Worn Compressor Clutch

The clutch connected to the compressor pulley should engage when you turn on the air conditioning. The clutch does not spin when the AC is turned off.

The clutch may briefly click when you switch on the air conditioning before the belt and pulley spin.

The compressor must be serviced if the clutch does not engage or does so with a shrieking or whining sound.

The compressor clutch is a high-wear device; if worn out, it can cause a rattling during operation. Some vehicles need the clutch replaced, while others require the compressor rebuilt.

How To Fix It?

ac compressor in car making noise
Repair To car AC Compressor Making Noise.

By identifying the type of sound the compressor makes while idle, you can fix a car AC compressor making noise.

Each sound has a unique answer and degree of knowledge needed to solve the issue.

Check The Cooling System

When the air conditioner is on, you should examine the cooling system if you find the air is not as chilly as you remember.

There is a 90% likelihood of a structural failure if the cooling drops significantly, yet the noise remains.

A broken piston can be held responsible for those structural failures. You ought to swap them out.

A bad compressor is undoubtedly possible, but other AC-related problems could make the air warmer than usual. You can test it to find out if the air temperature is higher than it should be.

Repair AC Unit

Your car’s compressor mounting may cause any knocking or clicking noises you hear when the air conditioner is running.

Generally, the mounting bolts for these items will be loose. Fixing the AC unit is a wise decision.

Start the engine after lifting the hood. If the mounting bolts cause the issue, you will notice the loose component moving or shaking.

Use the appropriate wrench to tighten the mounting bolts, and then purchase a thread-locking compound to assist in solving the issue long-term.

Replace AC Compressor

The best step is to replace the AC compressor if the noise from the compressor continues even when idle after trying all the preceding methods.

The air conditioner compressor and the rest of the belt-driven equipment will be mounted in front of the engine.

You should consider changing the dryer canister as well. If you don’t, the system can freeze, requiring you to replace it later and shell out money for another recharge.

Spending a little more now will save you considerably more money later. It wouldn’t hurt to replace the belt as well.

Call Professional

The best way is to call an expert if none of the above options can assist you. According to your car’s make, specific tools are needed to repair the AC system.

We advise taking your vehicle to a reliable mechanic who can perform a particular job.

It only takes an hour or so because a few vehicles have compressors that are reasonably simple to access. Unfortunately, it can take hours for some modern automobile brands.

Some call for the removal of the radiator and radiator fans. Others call for the removal of drive axles.

In other cases, lowering the entire subframe is necessary to create enough space to remove the compressor from the engine compartment.


What Does A Bad AC Compressor Sound Like In A Car?

There is no precise definition of a bad AC compressor. A jammed serpentine belt would either come off or shatter.

Nonetheless, a grinding noise at idle will be if the pulley bearing is rough. It is time for AC service if you hear whirring, whining, screeching, or rattling noises from the AC compressor.

They create this sound when the compressor is worn out. Thus you might need to replace the compressor completely. Sometimes it implies your complete air conditioner needs to be replaced.

Can You Drive With A Noisy AC Compressor?

Driving when your AC compressor is damaged is not a smart idea. While driving your car with a damaged AC compressor without major repairs is occasionally possible, it’s not recommended.

A car with a broken compressor can be safely driven if the clutch and bearing are sound.

Because the belts also drive the power steering, alternator, water pump, and occasionally the fan for radiator cooling, noisy bearings, and a frozen clutch will prevent you from operating a vehicle.

How Long Will An AC Compressor Last?

The compressor should have a minimal self-life of around 20 years if the supply voltage is stabilized, there is enough ventilation, and no overloading.

Yet, it also depends on the usage and the kind of incoming supplies you receive.


Now that you know the causes, types, and remedies for AC compressor noise at idle, you can determine how to resolve your issue.

It is usually advisable to take any sounds originating from your car’s AC compressor carefully.

Since this advice can help you figure out the cause of the racket and how to cure it, the technician can go further into the problem if you cannot easily resolve it.

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