An air conditioner that’s making noise may indicate serious system problems, especially if the noise is louder than normal or new. If you cannot determine the cause of air conditioner noises, it’s best to call a professional for assistance.
Screeching or Squealing Sounds
If these noises are coming from inside your home, they may indicate a problem with the blower fan. Check the belt to make sure it’s in good condition and that there’s nothing hitting the belt or pulleys. If everything seems fine, it may mean that the fan motor needs lubrication or that its bearings have failed. Have it checked by an HVAC professional. If the noise is coming from outside, it could indicate a problem with the compressor.
Clanking, Banging or Rattling
Often, these air conditioner noises indicate loose hardware in the blower fan or air handler cabinet. Make sure mounts for the motor are tight and look for any other loose hardware or obstructions. If the sound continues, call an HVAC professional. Some banging or clanking can also be harmless and caused by metal ducts expanding when heated.
Fast Clicking or Tapping
Check the blower for objects stuck in or hitting the blades. Remove the object, if possible, to avoid damage to the fan motor, and call your contractor if the noise continues.
Periodic Clicking Noises
Clicking noises may indicate problems with the electrical contacts or relays if they come from near the compressor or the electrical panel. Have your system inspected as soon as possible.
Rattling Noises From Outside
Rattling noises from the compressor may indicate a problem with its motor. If it progresses to a loud scream, call your HVAC contractor immediately. Humming noises may indicate either a bad start capacitor or a failed compressor.