What Do The Different Car Aircon Noises Mean?


Mar 01st, 2021

What Do The Different Car Aircon Noises Mean?

Cars make lots of different noises, but as car owners, we’re not so good at describing them with words. That can lead to some very awkward conversations down at the workshop, especially if you try to recreate the noise yourself to your probably confused mechanic!

Now, there are far too many car noises to cover in one article. That’s why we’re going to narrow down and focus on the many different car AC noises instead.

Car Aircon 101

Don’t worry; we’re not going to go into too much detail about what a car aircon is or how it works. If you’re looking to dive deeper into that topic, you should read this article first.

Instead, we’re going to brush up on a few basic things that will significantly help you diagnose car AC noises.

Your car aircon is kind of like the AC you have at home. The one in your car has the same types of components, such as a compressor, evaporator, condenser, and fan. But here's where it gets interesting: your car aircon also has a belt that powers that compressor by turning its clutch.

That belt connects the AC’s compressor clutch to the crankshaft of the engine. So, whenever your engine is on, it’ll use that belt to provide power to the car AC system.

Why does that matter? Here’s a spoiler alert: that belt may be one of the things causing the noise you hear.

What Are Some AC Noises With Simple Fixes?

Here are some of the more typical AC noises that you may hear. In most cases, addressing these noises will only require a few simple fixes.

Squealing or Screeching

The first and most common car AC noise is squealing or screeching. That noise could happen at any time, though you may experience it more often in the morning when you're starting up a cold engine. The telltale sign is when the screeching starts or gets louder when you turn on the AC in particular.

As we mentioned in the last section, the belts you have under the hood also connect to the AC compressor. Squealing or screeching could be a clear sign that your serpentine or drive belt is starting to get worn out.

The fix is pretty straightforward: you only need to inspect and replace the belt that's making the noise. Your mechanic can get that done for you pretty quickly, but if you’re the more hands-on type of car owner, you might want to do it yourself.


Your car aircon cools down your car by circulating refrigerant gases throughout the system. However, the car AC can do its job effectively only if the correct amount of gas circulates throughout. Too much or too little refrigerant will start to cause problems.

Suppose you hear a buzzing noise coming from the car aircon; that's a sign that there might be too much refrigerant in your car AC system. Those excess gases don't come out of nowhere, so this may be caused by a technician putting in too much gas during your last servicing.

It would be best if you got this problem sorted out immediately. Firstly, having too much refrigerant will cause your car AC to feel too warm, as it can't do a proper job of cooling down the air. Second, it could also lead to damage to the compressor and other components.

The fix is pretty simple: the technician needs to release some of the refrigerants to ensure that only the correct amount is left. However, this is a time-sensitive issue, so you'll need to get it sorted out as soon as possible!

Knocking or Clicking

Knocking or clicking noises usually sound scarier than they are. Remember: cars and all of their components, including the car AC system, vibrate a lot. Over time, that could cause things like mounting bolts to come loose gradually. When that happens, you’ll end up hearing knocking or clicking noises coming from the AC system.

To fix this, all you (or the mechanic) have to do is tighten all the screws and mounts. At the same time, it would also be a good idea to visually inspect those mounts to see if they’re still in good shape or need replacements.


While knocking or clicking might not be such a big deal, the same can’t be said about rattling. There are many causes behind rattling noise coming from your car AC, including a failing compressor, compressor clutch, or even a problematic idler pulley. Fixing it might only require relatively simple fixes, though some repairs could be a bit more serious.

Here, it’s worth noting that the hot Aussie climate does contribute to failing AC compressors. To find out more about that, check out this article here. Simply put, if you hear your AC rattling and that noise gets worse when you accelerate, then you may need to get the entire thing replaced.

What Kinds of AC Noises Mean Serious Trouble?

When diagnosing car AC noises, you may come across one or more of the noises listed above. Among them, buzzing and rattling are the ones that you should be most concerned about. That’s because they could indicate serious trouble with your car AC system.

Don’t panic if you ever hear your car AC system making such noises. With a slight sense of urgency, you should get your car to the workshop as soon as possible. It’s also best to keep your vehicle aircon off on your drive there.

Just a Recap

To recap, a buzzing noise could indicate that the technician overcharged your car AC system with too much refrigerant. Firstly, that will make it difficult for your car AC to cool down, so all you’ll get is warm air coming out of the vents. 

More importantly, too much refrigerant could cause serious trouble by damaging the compressor and other components. That’s why you need to get it sorted immediately without wasting any time at all.

On the other hand, a rattling noise could indicate a failing compressor, compressor clutch, or idler pulley. Regardless of which one it is, you should address it quickly to prevent further damage to your car AC system or any related components.

To find car aircon parts for your car, check out the Marketplace or send us a request for auto parts. Enjoy either of these services free from Carpart.com.au. With the marketplace, you get to browse all sorts of auto parts listed and transact directly with the buyer. If you want to get several quotes for the exact automobile spare parts you need, then I suggest that you use the request parts button.

By Ray Hasbollah