5 Air Conditioner Sounds You Don't Want to HearYour A/C is full of moving parts, all of which make noise. While most air conditioner sounds are considered normal, it’s important to know which ones are cause for alarm. Here’s a list of five sounds you don’t want to hear coming from your A/C because they all signal a need for action. 

Rattling From the Outdoor Component

The fan within the compressor unit should not rattle during operation. A rattling sound can mean the motor is failing or a piece of hardware has become loose. The louder the rattle, the more serious the issue, and if it turns into a screaming sound, you may have an ailing compressor. Call a professional if you hear any of these sounds, including humming, which is a sign of a defective motor or a declining capacitor.


A noise reminiscent of a playing card in a bicycle spoke means something may be caught in the blades of the blower or something’s making contact with them while they move. While this is one of the less critical air conditioner sounds, it warrants investigating as the increased resistance can cause premature wear and tear on parts.

Repetitive Clicking

It’s normal to hear a clicking sound as your A/C turns off or on, but a repetitive clicking emitting from the control panel or outside unit can be a sign of a defective relay or a faulty electric control.

Screeching or Squealing

Motor bearing issues or a worn belt can result in a squealing sound from the blower motor. Belts should be replaced immediately before they break and result in stoppage of the blower.

Excessively Loud Banging, Clanking, Rattling or Thumping

Rattling is a warning sign that something is loose and should be tightened before further damage occurs. A loud banging sound means something is either disconnected or broken. Turn off the system immediately and call for service.

For more help diagnosing air conditioner sounds, call the experts at Stack Heating & Cooling. Since 1976, we’ve been providing quality service to homeowners in the greater Cleveland area.

Our goal is to help educate our customers in Cleveland, Ohio about energy and home comfort issues (specific to HVAC systems). For more information about air conditioners and other HVAC topics, download our free Home Comfort Resource guide.

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