Why AC Making Strange Sound

Women surprised by loud noise

We’re glad you’re asking this question because it shows that you recognize when something is wrong with your air conditioner. Modern ACs run quieter than ever before, and you shouldn’t hear much more out of your home’s cooling system when you’re indoors than the whir of a few motors and the occasional drip of condensate moisture. When a strange sound disrupts this placid environment, it often means something is wrong with the air conditioning system. It may be a reason to call us for AC repair in Houston, TX.

The sound you hear can tell you more specifically what’s wrong with your AC. We’ll look over the most common of these noises and see what might be going on. (Please don’t try to make any repairs on your own, however. You need experts to do the diagnosis and actual work.)

Hissing or Bubbling

These noises are warnings that an air conditioner is losing refrigerant to leaks along its refrigerant lines. The hissing sound is high-pressure gas escaping from the lines, and the bubbling is liquid refrigerant escaping. Loss of refrigerant will endanger the entire AC and cause the compressor to burn out, so call technicians as soon as possible to find the leaks, seal them, and restore the refrigerant to its original level.


Sometimes this is a basic problem: the latch of the HVAC cabinet door is loose. Make sure the door is firmly shut and see if this stops the rattling. But this noise can also warn of parts that are coming loose or have come loose because of the vibration of the unit. Loud rattling might indicate a loose part inside the blower, and this will cause extensive damage unless it’s fixed soon.

Shrieking and Grinding

These are noises coming from motors in dire trouble. The shrieking sound warns that the bearings in a motor are wearing down. Fast repairs are necessary to replace the bearings and prevent the motor from burning out. The grinding noise often means a motor that is burning out and will need to be replaced.


This loud banging sound often means that the blades of the blower fan are bent or the blower assembly is misaligned, causing the blades to strike the house. Shut off the power to the AC immediately and call us to have the unit repaired.


A repeated loud clicking sound when the air conditioner starts up usually means the unit is hard starting. This drains more power than necessary and it also may warn of a compressor that’s in trouble. The clicking sound can also come from failing capacitors. Capacitors usually need to be replaced at some point in an air conditioning system’s lifespan.


Something that sounds like the wind through the trees shouldn’t be coming from your AC. Fortunately, this is probably something you can take care of on your own: replace the dirty air filter. A congested filter will sometimes make this noise as the blower struggles to draw air through the filter.

At All Star A/C & Heating Services, our integrity is our best, most used tool in our bag. Call us for AC repairs in the Greater Houston Area.

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