AC making a strange noise?

What usually causes this

These are the common possibilities, not a diagnosis. A page cannot tell which one it is — that takes a technician testing the system.

Buzzing or humming

Commonly a failing capacitor, a worn contactor, or a motor struggling to start. A unit that hums without the fan turning shouldn't be left running.

Grinding or screeching

Worn motor bearings in the outdoor fan or indoor blower. It usually gets worse, and a seized motor can take other parts with it.

Squealing

A worn blower motor or, on older and commercial equipment, a slipping belt.

Rattling

Loose panels or screws, debris in the outdoor fan, or a fan blade out of balance.

Repeated clicking

A single click at start and stop is normal. Repeated clicking without the unit starting often points to an electrical or control problem.

Banging or clanking

Something loose or broken inside the unit, sometimes in the compressor. Switch off and call.

What you can safely check yourself

• Note exactly what the noise sounds like, where it comes from (indoor or outdoor), and when it happens — at start-up, during running, or at shut-off. That narrows diagnosis a lot.
• Look for sticks, leaves or debris in the top of the outdoor unit and clear anything you can reach from outside with the power off.
• Check that access panels on both units look fully fastened.

What we check when we get there

1. 1The technician listens with the system running, then tests the suspected component — capacitor, contactor, motor bearings, fan balance or compressor.
2. 2A noise is often the early warning before a failure, so catching it can turn an emergency into a scheduled repair.

What it is likely to cost

Electrical parts behind a buzz are usually inexpensive. Motors cost more, and compressor noise is a major repair. You get the price before any work.

Diagnostic / service call

$89

Capacitor replacement

From $179

Contactor replacement

From $189

Condenser fan motor

$449–$799

Blower motor

$549–$1,099

Prices are starting points for standard work in the Savannah area. Final price depends on the system and site, and is confirmed before work begins. Permits and code-required upgrades may be additional.

Questions people ask about this

Is a buzzing AC dangerous?

A brief hum at start-up is normal. Persistent loud buzzing, especially with the fan not turning, can mean an electrical part is failing. Switch it off and have it checked.

My AC clicks but won't start. What is it?

Often the contactor or capacitor, or the thermostat calling but a safety control stopping the start. It needs testing.

Where to go next