Diagnosis
That's the compressor trying to start but failing, likely due to a failed start capacitor or a locked compressor.
How to Fix It
Replace the start capacitor. It's a common failure point.
- Turn off power at the breaker.
- Locate the round or oval capacitor mounted near the compressor.
- Discharge it safely (short terminals with an insulated screwdriver).
- Note the wiring and microfarad (µF) rating, get an exact replacement, and install it.
If That Didn't Work
With power off, try manually turning the compressor fan shaft with a wrench. If it won't budge, the compressor is seized and the unit needs professional service or replacement.
Heads Up
Never touch capacitor terminals with power on. A bulging or leaking capacitor is definitely bad. If the compressor is seized, continuing to try can damage other components.