AC Won't Turn On: Safe Checks Before You Call

What to check when an air conditioner will not start, including thermostat power, breakers, drain safety switches, and signs that need professional service.

When the AC does nothing at all, work from the controls outward.

Safe checks

• Thermostat display is on and set correctly
• Thermostat batteries are fresh if applicable
• HVAC breakers have not tripped
• Air-handler service switch has not been turned off
• There is no obvious drain-pan overflow condition

If a breaker trips again after one reset, leave it off and arrange service. Repeated resetting can mask an electrical problem.

Related: thermostat service and emergency AC repair.

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