A bad AC compressor can make a variety of different noises, from clicking and grinding to whining and humming. The specific noise your compressor makes can be an indicator of the problem it is experiencing.
If you hear any strange noises coming from your AC compressor, it’s important to have it checked out by a professional as soon as possible.
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:
- Grinding noise
- Growling with the AC compressor engaged
- Growling noise with the AC compressor disengaged
- Rattling Noise
- Squealing Noise
- Whistling Noise
- Banging Noise
- 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.
How do I check my AC compressor?
One way to check if your AC compressor is working is to feel the air coming out of the vents. If the air is cool, then the compressor is likely working.
Another way to check is to listen for a clicking noise when you turn on the AC. If you hear a click, then the compressor is probably working.
Finally, you can check the pressure of the refrigerant using a pressure gauge. If the pressure is low, then the compressor may not be working properly.
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.
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.
AC Hissing Noises
If your AC compressor is hissing, there are a few potential causes. One possibility is that your compressor is low on refrigerant. This could be due to a leak in your system, or simply because it needs to be recharged.
Another possibility is that there is an issue with one of the valves in your compressor. If a valve is stuck open, it can cause a hissing sound.
Finally, if your compressor is worn out or damaged, it may also start to make strange noises. If you’re not sure what’s causing the problem, it’s best to have a professional take a look at your system.
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.
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.
Meet Mike O’Connor, (a DIY enthusiast), living in Cincinnati, a city ranked as the noisiest in the USA.
As a work from home dad, I have a first hand experience of how noise can truly affect your well being.
Soundproofing isn’t something that should be taken as a hobby, it should be a skill that every homeowner should be equipped with.
Most of the work documented on this blog comes from purely first hand experience, and the products recommended work as indicated.