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Hometown Heating and Air Conditioning Blog

What’s Causing That Annoying Noise From My AC?


We’re well into spring and by now, you’ve probably had a chance to determine how well your air conditioner is doing so far this season. How would you rate its performance? Is it quietly and efficiently cooling your home down to your desired temperature? Or does it seem like it’s taking longer than usual?

A surefire way to tell if your AC is struggling is to give it a listen. Just like any complex piece of machinery, your AC will make noises when it’s having a hard time doing its job. Booming, hissing, screeching, and bubbling are all annoying noises you don’t want to hear from your AC. Let’s go over each one and what the possible cause is.


If your air conditioner makes a loud boom, it can be startling indeed! Don’t worry, this noise doesn’t mean your AC is about to explode or take off to outer space. A booming AC means that it’s hard starting or struggling to turn on and then it “booms” when it finally does. This is a sign that it’s struggling to power the compressor and requires an HVAC technician to inspect it. 


No, your AC isn’t made at you. Hissing noises occur for the same reason they occur in just about any other piece of equipment: something is leaking from somewhere. Where you’re hearing the hissing sound will help determine what the issue is.

The leaky substance could be refrigerant somewhere along one of the lines. You might also hear a bubbling noise if it’s a refrigerant problem. If you hear the noise when you’re by the outdoor unit, this is potentially hazardous. It could mean that the pressure inside the compressor is too great and should be looked at right away.

Shrieking, Grinding, Metal-On-Metal

These unpleasant noises are cause for alarm. They usually mean either one of two things. There could be a lack of lubrication between the moving metal parts. This will result in the grinding noise you hear. Or it could be a part such as the blower fan or fan blade that has come loose and is smacking other metal parts of your air conditioner. 

Another possible issue is with the outdoor unit (the compressor). The grinding noise could be caused by the pistons that compress the refrigerant gas. This noise will result because the compressor has worn down and can no longer function. Unfortunately, this usually means that the compressor needs to be replaced entirely and depending on the age of your system, it might be more cost-effective to replace the entire AC.

Banging and Clanging

These noises could be as simple as a loose, metal part such as a screw or bolt that’s banging around the interior of the AC. You might also hear this sound from the air ducts. Banging and clanging are common noises heard from your HVAC system’s ductwork. It’s caused by the expansion and contraction of the metal duct walls as pressure and temperature in the system increase and decrease. You’ll hear it any time your AC or heater is running.

Please don’t hesitate to reach out to the team at Hometown Heating and Air Conditioning to discuss your AC’s performance! Your comfort is our business.

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