Air Conditioner Compressor Rattling Noise: Causes and Fixes

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Is your air conditioner compressor making rattling noise? Rattling noises is one of the eight most common sounds an AC compressor makes.

A little noise from the outdoor air conditioner unit is just fine, but loud rattling noises should cause concern.

Rattling noises transform what was once a quiet air conditioning unit into a mess that not only interferes with the HVAC efficiency but also makes your home a noisy mess denying you a peaceful and quiet living.

In this guide, I shall take you through some of the causes of air conditioner compressor rattling noise and how to fix this problem.

Rattling, banging, or clunking noises as the cooling kicks is an indicator that there are loose parts. When a screw comes loose, the air conditioner compressor doesn’t sit tightly to its mounting, and it’ll produce sounds as a result of its movements. Tightening the mounting should be the first step in eliminating the noise.

Air Conditioner Compressor Rattling Noise Causes

Rattling noise is one of the initial signs of a mechanical breakdown. Therefore, it’s important to understand the possible reasons why your AC unit could be making noises.

I have divided this article into two sections to diagnose rattling noises in-home AC and in-car AC units.

  • AC compressor rattling noises for home conditioning units
  • AC compressor for car AC


Because the outdoor air conditioning unit is often located outdoors, it is prone to debris and dirt accumulation. Rocks, leaves, small sticks, and even small insects will pass through the vents in the unit, making the unit their new home.

Leaves and small sticks can get caught in the outdoor unit fan. The fan will try to spin regardless of the blockage, which often results in rattling sounds.

Cleaning the outdoor unit is a simple fix that you can do in less than 10-20 minutes. Simply unscrew four screws to remove the venting cover of the outdoor unit.

Get rid of any visible debris and use a damp cloth or towel to clean dust from the unit. Once down, return the cover in place and tighten the screws back.

Be sure that the outdoor unit is not located in areas where it’s likely to catch heavy debris such as rocks or pebbles because they can bend or break the fan blades.

Misaligned Fans & Broken Fan Cage

Because AC fans continuously spin when the AC is turned on, they can misalign with time, resulting in the blades hitting the side of the air conditioning unit.

What at first seems to be a normal rattling noise resulting from a misaligned fan can result in a bigger problem that could actually call for an expensive repair.

For example, misaligned fans continuously hitting the fan cage can eventually break it hence causing the need for fan cage replacement.

Broken Motor

Air conditioners often have two motors, one on the outside unit and the other one on the indoor unit.

If one of the motor units stops working, your air conditioner will make rattling noises. Motors often have bearings that, with time, need to be lubricated for proper functioning or replaced when worn out.

Air compressors have motors, and when the motor parts malfunction, it can result in loud rattling noises. At this point, your AC won’t be working effectively as it used to.

Loose Parts

Air conditioning components are often held in place with screws. When one of the screws becomes loose or falls out, it can result in rattling sounds.

When the panels aren’t held together tightly, it can also result in rattling sounds. You should always inspect for loose parts and tighten any loose screws.

Loose parts could also result in banging or clunking noises that occur when the air conditioning system runs.

When a bolt comes loose, and the compressor isn’t held tightly in place, the compressor is bound to make sounds due to movement.

Components inside the compressor such as pistons, rods, and other parts can become loose, producing rattling sounds when the compressor runs.

In this case, compressor replacement is required to fix this noise problem. This is because it’s easier and cheaper to replace a compressor than it is to repair the internal components.

Car Air Conditioner Compressor Rattling Noise Causes

Just like your home air conditioning unit, your car air conditioner is also bound to produce rattling noises due to different causes.

The common causes include:

Failing AC Compressor

Before Freon, which is responsible for blowing cool air into your car cabin, can be pumped in the condenser, it requires to undergo intense pressure.

The air compressor is responsible for creating this high- and low-pressure difference, and with time it’s subjected to wear and tear, requiring replacement.

A failing AC compressor will produce rattling noises. And as earlier mentioned, a compressor replacement is much cheaper and more effective than repair.

Regular inspection and servicing can significantly increase the lifespan of your car’s AC compressor.

But usually, you can expect your AC compressor to last 8-10 years, and for most people, that’s usually the same as the car’s lifespan.

Bad Idler Pulley

Idler pulleys are designed to connect, guide, and provide tension for engine drive belts that operate with your car’s engine.

The serpentine drive belt that connects the engine to the AC could just fine with only the idler pulley requiring replacement.

Idler pulley replacement is a reasonably cheap fix.

Worn Out Serpentine Belt

The serpentine belt is responsible for driving different car accessories such as the air pump, alternator, power steering pump, air conditioning unit, and more.

The drive belt is prone to wear and tear with time resulting in poor tension and loud sounds similar to squeaking or rattling.

Inspect the serpentine belt for any visible signs of wear and tear- see if you can spot any cracks or broken inner ribs which can cause the belt to slip.

A worn-out compressor clutch can cause rattling noises. In some cases, only the clutch needs replacement, while in others, you need replacement of both the clutch and the compressor.

On Air Conditioner Compressor Rattling Noise

Air conditioners play an essential role in keeping our homes and automobiles cooler during those hot sunny days.

Unfortunately, due to wear and tear on various components, these vital units are bound to produce noise as they deteriorate just like any other appliance would.

Above are the different causes of AC compressor noise and the possible fixes required. It’s important to note that in some cases, rattling noise doesn’t always translate to a problem with your AC, as other components can cause rattling noises.

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