Strange HVAC Noises: What They Mean
Your HVAC system should be relatively quiet. New noises are an early warning.
Common causes
Squealing or screeching
Often a belt, bearing or motor problem.
Banging or clanking
Loose or broken parts.
Buzzing or humming
Electrical issues such as a failing capacitor or contactor.
Clicking at startup
Normal at start, but continuous clicking can indicate an electrical fault.
Hissing
May indicate a refrigerant leak or air leak.
Rattling
Loose panels, debris or ductwork.
What you can safely check
- Turn the system off if the noise is loud or sudden.
- Check around the outdoor unit for debris.
- Check for loose panels you can safely see.
When to call a professional. Call a technician for any persistent or loud noise. Never open electrical panels or remove access covers on equipment. If you smell burning or see smoke, turn off power and call 911 if there is any danger.
Is a noisy AC dangerous?
It can be a sign of damage that gets worse. Do not ignore it.
Why does my AC buzz?
Often an electrical problem. Turn off the system and call us.
Can maintenance prevent noises?
Regular maintenance finds worn parts before they fail loudly.
Next steps and related help
Comfortable again, without the runaround
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