HVAC
Why Is My AC Not Turning On? 8 Things to Check
When an air conditioner will not start, check the thermostat, power, filter, and obvious system controls before arranging service.
What to check
Confirm the thermostat is actually calling for cooling
Set the thermostat to Cool and choose a temperature below the current room temperature. Confirm the display is active and responds to input.
Check the AC circuit safely
Check the home's relevant breaker only from a safe position. If a breaker trips again, do not repeatedly reset it.
Check the indoor unit power switch
Make sure the indoor unit's service switch has not been accidentally turned off, if your system has an accessible switch.
Check airflow restrictions
Inspect the air filter and replace it if it is heavily dirty and due for replacement.
Allow for a normal startup delay
Wait several minutes after changing thermostat settings because some systems have a built-in startup delay.
Compare indoor and outdoor behavior
If the outdoor unit does not run while the indoor blower does, the system may need professional diagnosis.
Stop when the symptoms point to a component failure
Do not open electrical panels or work on capacitors, wiring, or refrigerant. Call an HVAC professional for persistent no-start conditions.
When to call an HVAC professional
Call an HVAC professional when the AC remains unresponsive after safe thermostat and power checks, a breaker repeatedly trips, the system has water damage, or the problem points to a capacitor, contactor, wiring, compressor, refrigerant, or control-board issue.
Quick checklist
- Thermostat display is active.
- Thermostat is calling for cooling.
- Startup delay has passed.
- HVAC breaker has been checked safely.
- Accessible service switch is on if applicable.
- Indoor and outdoor behavior has been noted.
- No active water or electrical hazard is visible.