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What Does a Bad Ac Compressor Sound Like?

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What does a bad AC compressor sound like? A bad or failing air conditioner compressor will make all sorts of noises, and each is an indicator of a different problem that needs fixing as soon as possible. (Read my guide on quietest air conditioners on the market)

To be precise, there are eight different types of sounds that a bad air conditioner compressor makes.

These noises indicate that the AC compressor needs repair/service or a complete replacement. They include:

  1. Grinding noise
  2. Growling with the AC compressor engaged
  3. Growling noise with the AC compressor disengaged
  4. Rattling Noise
  5. Squealing Noise
  6. Whistling Noise
  7. Banging Noise
  8. Knocking Noise

Even with the best quiet air compressor, failure to undertake routine annual maintenance can have devastating consequences.  

In this guide, I shall be focusing on the different sounds that an air conditioner compressor makes and the possible fixes that need to be done.

What Does a Bad AC Compressor Sound Like?

What Does a Bad Ac Compressor Sound Like?


AC Compressor Knocking Sounds

When you hear knocking sounds from your car air conditioner compressor, it indicates internal compressor damage.

This problem is most common in piston-type compressors.

But knocking noises don’t always translate to a damaged ac compressor. The knocking could also be an indicator of loose AC mounting, or it could also indicate that other parts of the AC units aren’t tight enough.

Therefore, it’s important to inspect for loose mountings before condemning your car’s AC compressor.

Often, the loose parts will shake and rattle, and you can hear a racket if you kick the AC.

To fix this problem, you’ll need to stop the engine and open the car hood to expose the AC. Inspect to see the parts that are shaking and tighten the component till they stop.

You may need to include thread locking substances such as the Loctite Threadlocker to the parts to prevent them from loosening in the future.

If the knocking sounds don’t stop after tightening the parts, it could be that the compressor is damaged and needs replacement.

But don’t rush for a replacement before troubleshooting all other noises discussed below.

Knocking noises could also indicate incorrect pressure, refrigerant system blockage, or internal damage to the compressor.

Buzzing Noise

Do you hear the car AC compressor making a buzzing noise when you first turn on the car air conditioner or while accelerating?

If that’s the case, then you could be having too much Freon in the AC system.

The excess Freon could be as a result of a routine service you did in the past few weeks, or it could be as a result of an overcharged AC, meaning that the refrigerant could be entering the compressor intake port.

As a result, the AC won’t function as intended. It won’t cool your car, which could result in serious damage to the car ac compressor or damage to other parts of the car AC.

I would highly recommend you get your car inspected as soon as possible.

Car AC Hissing Noises

Hissing noises is one of the most common noises that most drivers often complain about regarding their car AC.

The hissing sound is often heard when you shut your car off.

This shouldn’t frighten you as the hissing sound from the ac doesn’t often translate to trouble with the AC.

Hearing hissing noises after turning your car off is just a sign of equalizing pressure.

So how does this happen?

When your car AC is running, a low-pressure side and high-pressure sides are created. The coolant, which is in most cases Freon, moves between these two pressure sides that are divided by either an orifice tube or an expansion valve.

Switching off your car causes the freon gas to move from the high-pressure side of the AC compressor to the low-pressure side hence equalizing the pressure.

Even though the AC pump hissing noise is normal, hissing at other parts of the car is just a solid reason to visit a professional mechanic as soon as possible.

Screeching/Squealing AC Noises

Loud screeching or squealing noises is one of the most common noises drivers hear with a malfunctioning AC.

This problem is often associated with the serpentine/drive belt.

What is a serpentine belt responsible for?

The serpentine belt helps turn the pulley on your air conditioner compressor, which in turn pressurizes the refrigerant lines allowing for cool air to enter your car cabin.

The squealing noise is one of the easiest noises to diagnose. You will need to inspect the drive belt for visible signs of wear and tear like missing ribs or cracks before taking the car to a qualified mechanic.

Squealing noise doesn’t always indicate a problem with the serpentine belt. Failing bearings in the compressor pulley make noises similar to squealing, grinding, or roaring.

Therefore, inspecting the serpentine belt first will always keep you one step ahead before making a conclusion.

AC Compressor Rattling Noise

Did you know that the engine comes under “load” when you run the AC?

Therefore, rattling noises can result from a number of issues, including a failing catalytic converter or a failing steering pump pulley. Here’s my guide on fixing power steering pump pulley rattling noises.

For a rattling emanating from the catalytic converter, check out this detailed guide on how I fixed my rattling catalytic converter.

However, when you turn on the car AC and hear rattling noises, there are three possible culprits. They include:

Air conditioner compressor: if your ac rattles or makes humming noises that worsen as you accelerate, these are signs that you will need AC compressors replacement in just a few week-months.

Idler Pulley: If the idler pulley is making rattling noises, it could result from failing bearings. The idler pulley with failing bearings will start making rattling noises when the AC compressor is engaged.

Compressor Clutch: This component is prone to wear and tear and often calls for a regular replacement, especially if you are constantly running your car’s air conditioner.

The compressor clutch is responsible for pressurizing the AC and helps pump the refrigerant. Rattling noise from this part calls for the replacement of the worn-out clutch. In some rare cases, your entire compressor may be replaced.

What Does a Bad AC compressor Sound Like?

As you’ve read from my guide above, a failing AC compressor will produce different sounds, with each requiring a different fix.

Some of the noises you hear don’t often translate to a bad compressor. It could be a problem with other components of your air conditioning system that need a simple repair or complete overhaul.

Diagnosing these noises will go a long way in helping you pinpoint the exact problem with your car air conditioning system.

Have any tickling question that needs answers? Just let me know in the comment section down below.

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