Window Air Conditioner Noise (Clicking, Buzzing, Rattling) & How to Reduce it

Knowing what is causing window air conditioner noise and how to stop it will be music to your ears.

This guide covers the major causes of noise like AC compressor noise, the unit making noise when off and a list of specific window air conditioner noises like a clicking noise, buzzing noise, rattling noise and more.

And you’ll learn how to stop the noise, if it is a problem that can be repaired or solved in another way. These include sound insulating options for ACs that just happen to be noisy even when working as they should.

Window AC Compressor Noise

Window AC Compressor

This is often the most concerning kind of noise, but the compressor is the “heart” of the unit. If it goes, and you’re in a position to make the repair, replacement is the cost-effective option.

Common compressor noises include clicking noise, thumping perhaps, buzzing noise and rattling noise.

But it isn’t always the compressor – or it could have an easy fix. This noisy AC issue could easily have been considered a “dying AC compressor noise,” and the compressor was involved, but the solution was cheap and easy.

Later sections discuss diagnosing and then reducing noises.

AC Making Noise When Off

This might seem unusual, but based on the search traffic it gets, apparently a lot of AC owners experience it. And most of the answers given online are inaccurate.

This is usually an electrical issue – even if the AC is turned off, it is still getting power when plugged in. And a buzzing noise is most common.

1). Bad Relay Switch: This switch regulates power to the compressor, and if it has failed, its amperage is off, and it might buzz.

2). Worn or Frayed Wiring: A buzzing noise can result or possibly a clicking noise.

3). The Fan Making Noise: A bad or failing fan motor often makes a buzzing noise.  

Window AC Making Noise – Other Sounds and Causes

There is a section on diagnosing and solving problems below, but often just knowing what’s wrong presents an obvious solution. Something is loose? Tighten it. Something is crackling or whistling? Clean the air filter and coil. Etc.

Buzzing Noise: A wiring issue as discussed above. The AC will buzz when it is running too, if it is having one of those issues. 

Crackling Noise: Also popping noise, cracking noise. The unit is freezing up because it isn’t getting sufficient airflow or you’ve set the thermostat at or near its coldest setting. See if running the fan only for a while allows the ice to melt. Otherwise, give the air filter and coils a thorough cleaning.

Clicking Noise: Why is a window AC making a clicking noise? Once the AC shuts off, the back side of it – the outdoor parts – are quite warm from dispersing hot air. Metals expand. As they cool, metals contract, and that causes clicks.

Rattling Noise: Or banging. Something is loose – often the nut holding can be the cause of the fan making noise. Or perhaps a mount for the compressor or fan has been vibrated loose. When the mounts get loose, the compressor or fan can also bounce around, contact other parts and make a lot of noise.

Chirping Noise: In older ACs this is a sign of a dry bearing. Sometimes it means the fan is out of balance and is lightly contacting another metal part on each revolution. It might sound like squeaking or a whining noise too.

Pulsating Noise: Or pulsing. These sounds are generally the normal working of the compressor. It might be bothersome, and later we discuss how to quiet a noisy window air conditioner, but it likely doesn’t signal a repair need.

Gurgling Noise: This one may or may not be normal especially. If the unit is new and has always done it, you’re probably hearing normal noises related to condensation and draining.

The AC takes humidity out of the air, and it runs out the back of the unit, which might sound like gurgling or water running.

If it is a new noise, the condensate pan or drain could need cleaning. If water is backing up, this is your answer.

The major causes are ice melting off the indoor  coil. Ice forming on the coil could be normal. But ice is often the sign of a dirty coil that needs vacuuming and washing off. And the air filter likely needs cleaning too.

Restricted airflow prevents the coil from warming enough to prevent condensation from freezing on it.

Another water noise is a rain noise – trickling or dripping – and it is almost always condensate dripping onto the ground outside. Totally normal.

How to Reduce Noise from Window Air Conditioner

Steps to diagnosing a window air conditioner and potentially solving the noise are:

1). Pull out the filter. If it dirty, wash it. Might relieve gurgling, hissing, low humming noise, clicking or crackling noise.

2). Remove the cover.

3). With the unit ON, check where the noise is coming from. You might find the source of something loose and making a rattling noise, knocking or bouncing. Tighten it up. Or like in the video linked to above, if parts are making contact, isolate them to eliminate the noise.

Or you might be able to determine what part is buzzing or where wiring is loose or frayed and needs to be repaired. Replacing a relay or even a compressor is probably within the skillset of a handy person.

4). Clean the coils. Vacuum them, and then hit the coil with a spray cleaner designed for coils. Spray off the coils. Might fix a gurgling noise, cracking, whistling or pulsating.

5). Clean the drain pan. Flush out the condensate line, if possible. Dirt and clogs are often the cause of gurgling or water noises that aren’t normal functioning.

6). Put the cover back on the unit, and give wet coils 30-60 minutes to dry.

7). Reinstall the unit in the window, and turn it on. Let it run long enough to start making noise again.

How Can I Fix a Noisy Air Conditioner?

If the main problem is that your AC is just a real noise maker even when functioning normally, you might still be able to muffle the noise.

Consider trying window AC insulating panels like those produced By Duck Brand. They’re thicker than the flimsy wings that come with most units. And put something like an Air Conditioner Weather-seal around the unit. Both products and those like them can muffle general noise and limit vibration noise.

Does a window AC silencer work?

No. They are not readily available anymore – we couldn’t find one from any online retailer. The problem is that they would surround the entire outside of the unit, reduce too much of the airflow, and the ACs wouldn’t cool as well or efficiently. Sometimes the lack of airflow caused mechanical failure.

What Are the Quietest Window ACs?

Sometimes the only solution is to buy one of the quietest window ACs available. There are some on the market that have inverter compressors– proven to run 50% than standard compressors – around 45 decibels compared to 65-70.A second option is to buy one of the quiet window AC designs that allow you to close the window more of the way, a sure way to reduce noise getting into your home. A few are also equipped with the inverter-driven compressor style for quiet operation.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications. Protection Status