What is That Sound Coming From My AC?

Trane HVAC system

If your AC is making unusual noises, you may find yourself calling your local HVAC company in Phoenix, AZ, for AC repair services in the near future. While air conditioning units tend to make some noise while running, especially the part of the unit that lives outside,  others can be a harbinger of AC repairs coming down the pipeline. The potential seriousness of the problem depends largely on the sound you hear. A rundown of AC noises to listen for can help you determine what’s going on and whether you need to reach out for repair service.


While a light whooshing sound is completely normal from any AC, a hissing sound is usually an indicator of trouble brewing. Light hissing can indicate an internal valve leaking. The hiss will gradually grow louder and make a horn-like noise and will probably be more noticeable when you are powering the unit down. Loud hissing is a good indicator of excess internal pressure on your unit’s compressor, which can become dangerous. If you hear it, power the system off and reach out to your HVAC company immediately.

Buzz! Rattle! Bang!

Any one of these sounds can be an ominous sign for your AC. Buzzing can mean anything from an electrical problem to a refrigerant leak. Rattling and banging are generally symptomatic of a broken internal part in your unit. All of these require professional help ASAP.


High-pitched squealing from your AC? A broken belt on the inside of the unit’s fan is often the cause. The same noise can come from a worn-out motor bearing — as the bearings go bad, they emit a squealing noise.

Remember, some noise from your AC is completely innocuous. The condenser on your exterior unit emits a gentle hum, which is often heart while the unit is running. If your AC is older, it is probably noisier than a newer unit would be. If a noise from your AC bothers you, stave off bigger problems by having it checked out sooner rather than later. 

Don’t second guess what’s happening with your AC unit. Reach out to AAA Cooling, your AC contractor in Phoenix, AZ, to keep your system up and running in optimal condition.