Have you ever flipped on your AC on a hot summer day only to discover that it’s suddenly making a knocking or clicking noise, or possibly rattling, grinding, vibrating, or buzzing noises? These sounds when you turn on the car’s air conditioner can be enough to send you into a panic. For those of us living in particularly scorching parts of the country, a broken car ac system sounds like a nightmare. A healthy and good working air conditioning system should be relatively quiet and unobtrusive. If your car AC is making noise, determining what type of noise is coming from your system will bring you closer to diagnosing the root of the problem. Is it a worn clutch, a bad compressor, a faulty hose, or loose component mounts?

Car AC Making Noise?

What many may not know is that a vehicle’s AC is controlled by what’s called a serpentine belt. A serpentine belt is a long, rubber belt that transports power to the engine accessories. The parts that make up this belt include an alternator, tensioner, water pump, power steering pump, crankshaft pulley, idler pulley, and AC compressor. If this belt breaks, it can mean that everything stops working, including your air conditioning. It can cause your battery to die and the engine to overheat.

With this in mind, it’s imperative to get your serpentine belt replaced on a regular schedule. Doing so can save a lot of time, money, and hassle. Now with a general understanding of this essential belt, let’s get down to why your car AC is making noise.

Clicking or squealing

AC clicking when you turn it on? A quiet clicking sound can be normal. However, if it’s loud and rapid, it could mean the clutch is worn. If clicking is a common occurrence, you may have foreign matter interfering with the blower motor.

A quick YouTube search can show you just how to inspect your blower motor if this is the case. In extreme cases, your AC may be starting to squeal. This can be an indication that the clutch is at the end of its life. It may also mean that it’s contaminated with oil or the pulley is faulty.

Vibration sounds

Can you detect a vibrating sound coming from the cabin when you turn your air conditioning on? This can mean that the hose is rubbing against either another hose or something else in the engine compartment. If scratching or rubbing spots are present when you check under the hood, you can reroute the hoses with cable ties.

Rattling and knocking

When it comes to noises like rattling or knocking, they can come and go. This can indicate loose or damaged mounts. The mounts and bolts may need to be either replaced or tightened in this case. They also may be coming from inside the compressor.

If the noise gets louder when you hit the gas, it can mean the compressor needs to be replaced entirely. Checking the health of your drive belts may be necessary. The clutch, the pulley bearings, and the blower motor may also be the culprits with rattling and knocking noises.


AC buzzing like a bee? This may point to a system that’s been overcharged with refrigerant. This can mean the refrigerant may be entering your compressor intake port. The refrigerant entering your compressor intake port can lead to poor cooling and damage to components. This is definitely an issue that should be addressed ASAP as you may need to end up replacing the compressor altogether if not done soon enough.

Whistling and hissing

Fortunately, whistling and hissing aren’t something to be concerned about, so don’t fret! It’s a sound that may happen after the AC’s been turned off. This happens when high pressure and low-pressure areas equalize as refrigerant moves through a metering component. Basically, when turning off your car, freon will move from one side of the compressor to another.

Local Auto Body Shop AC Repairs

It’s quite difficult to come across an AC system completely devoid of even the tiniest of noises. Determining what exactly the noise sounds like and how loud it is can help you diagnose the root of the problem. If your vehicle has started to make any of these noises, it’s time to either break out the repair manual or take it to a trusted local auto mechanic. It’s also important to make sure your serpentine is functional and up to date. This will all ensure that you don’t damage your trusty AC system even further.

Additional Reading: When to Replace Your Serpentine Belt

Dave & Rays Automotive Repair Shop in Omaha, NE

Our team has learned one thing: automotive problems are as varied and unique as the customers who bring them to us. Fortunately, our decades of experience in auto service and repair also mean that our skilled network of professionals is ready to accommodate an impressive scope of automotive issues. Contact us today.

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