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Quiet Down, Already! A Guide to Common HVAC Noises

The only noises your HVAC system should make are a blowing noise when air comes out of the vents and perhaps a click or two when the heat or AC first turns on. If there are any other loud, unpleasant noises keeping you up at night, you don't want to ignore them! They're usually a sign that something is wrong with your HVAC system, and, if you don't address the problem quickly, it's just going to get worse. Here's a look at some common noises and their causes.


If there's a sound that mimics that of brakes screeching or wheels squealing, you probably have an issue with your blower motor. There's a belt that goes around the motor, and when this belt becomes worn, it tends to make this type of noise. The good news is that all your HVAC technician should have to do is replace the belt – as long as you call them soon. If you let your furnace operate with a worn belt for too long, the motor may overheat, and you may need to have the entire thing replaced.


Rattling noises are usually caused by loose ball bearings in the motor. Once again, this is an easily resolved issue, but it can cause the motor to fail if not addressed. Sometimes the rattling may simply be due to a loose screw or bolt. If you're confident in your basic repair skills, you can turn the power off to the furnace, remove the cover, and check all visible bolts to ensure they're tightened before calling your HVAC technician.

Constant Clicking

There should be a click or two when the furnace first turns on. This is the sound made when the thermostat relays the message to "turn on" to the furnace. If you're hearing repeated clicking noises, there's probably an issue with either the thermostat or the wiring between the thermostat and furnace. You can try replacing the batteries in your thermostat, as this is occasionally to blame. You may also try turning the power off to the thermostat (at the breaker level), removing it from the wall, and ensuring that all wires coming into the thermostat are firmly fastened. Restore power, and turn your heat back on. If the clicking still happens, your HVAC tech may need to re-wire your system or replace your thermostat completely.

If you hear any other strange or suspect noises coming from your HVAC system, make the call to your HVAC company sooner rather than later to reduce your chances of needing extensive repairs.