Outdoor condensing unit with a large fan on a steel stand
Generic photo: ready made · Pexels License

Central AC won't come back after a power outage or breaker trip

After power returns, thermostats and some outdoor units hold off the compressor for a few minutes. If nothing starts after that, check the thermostat, both breakers, the outdoor disconnect, the float switch and the low-voltage fuse before suspecting parts damaged by a surge.

Cross-checked ~30 min easyBrands: All

Before you start

  • Outdoor disconnect and contactor carry 240 V: caution.
  • Reset a tripped breaker only once; a repeat trip needs diagnosis.

Diagnostic steps

Unlock all 5 steps with expected values

Full library + AI assistant for $34.90, one time.

Get lifetime access

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

More air conditioners guides

Guide · Air Conditioner

PTAC not cooling (fan runs, air not cold)

Most PTAC no-cool calls are airflow (filter, coils), a wrong control setting or a failed compressor start component. Rule those out before suspecting the sealed system.

6 steps ~60 minmoderate
Guide · Air Conditioner

PTAC not heating (electric heat or heat pump)

PTACs heat with electric strip heat, a heat pump, or both. Heat pump models switch to strip heat in cold weather. Check settings, then the heater element and its limits, then the reversing valve.

5 steps ~60 minmoderate
Guide · Air Conditioner

PTAC error codes: how to read and clear them

Most PTAC brands store fault codes that can be shown with a button combination on the control (for example GE Zoneline uses a MODE + another key sequence on some models). Read the active code, fix the cause, then clear it.

4 steps ~20 mineasy
Central AC won't come back after a power outage or breaker trip · OnCall Tech