5 Common AC Noises and What They Mean

Nothing is worse than hearing a terrible noise from your air conditioner and having no idea what it means. Will it go away on its own? Should you turn off the unit and call for an emergency service? Is it something you can fix yourself?

Here are the most common air conditioner noises, what they mean, and what you should do next. When in doubt, always call an HVAC contractor. A loud and unfamiliar noise coming from your AC unit is never a good thing.

1. Screaming/Hissing

If you hear a loud, high-pitched hiss or scream coming from your air conditioner, you should shut off the unit immediately. A common culprit is a refrigerant leak or problem with the compressor. This should not be ignored as refrigerant can me harmful to your health and seriously damage your unit. If the leak is large enough, you may hear a gurgling noise as well.

2. Squealing

Just like cars, your air conditioner can make a squealing noise when the fan belt is damaged or misaligned. This does not inhibit the unit from cooling your home so you can keep your unit running if you hear this noise, but we recommend calling for a repair as soon as possible. This problem could lead to a domino effect of other repairs, so don’t wait!

3. Buzzing

A buzzing or humming noise could mean an issue with the compressor, electrical wiring, refrigerant line, or a loose part. Because the problem is not obvious, it is always best to call an HVAC contractor to take a look. Especially if it sounds less like a rattle and more like a buzz, it could be a very serious problem.

4. Clicking

It is normal to hear clicking when the AC unit starts, but if the clicking continues after startup, start by cleaning the outdoor AC compressor. There might be debris making this clicking or rattling noise. A clicking noise can also indicate a bent fan blade or an electrical issue, so if you do not feel comfortable fixing it yourself, call an HVAC technician.

5. Banging

A banging noise is usually a sure sign of a loose or broken part, oftentimes being the compressor, fan, connecting rod, piston pin or crankshaft. Sometimes the part simply needs to be tightened, other times the part will need to be replaced. We recommend calling an HVAC contractor to inspect the unit as a loose part banging around could be causing more damage.


If you are near us in Aurora or live anywhere in the Denver Metro Area, Grand Home Services would be happy to answer your questions or help you with your AC unit. Call 720-365-1187 or contact us online today!