Short answer
If your AC will not turn on, check the thermostat mode and batteries, the breaker for both the indoor and outdoor units, the outdoor disconnect switch, and whether the condensate safety switch has tripped. If everything checks out and the outdoor unit hums but the fan will not spin, a failed capacitor is a common cause that a technician can replace.
Thermostat
Set to Cool and several degrees below room temperature. Replace batteries.
Power
Central AC usually has two breakers, one indoor and one outdoor, plus a disconnect box next to the condenser.
Not sure it is safe to keep running? A local technician can check it today.
Call NowCondensate switch
A full drain pan or clogged line trips a float switch that cuts power to the AC.
Humming outdoor unit
A hum with no fan usually means a bad capacitor or contactor. Do not open the unit yourself; capacitors store dangerous charge.
Related questions
Can a capacitor fail in hot weather?
Yes, heat is the most common cause of capacitor failure.
How long should I wait after a power outage?
Many systems have a 5-minute delay before restarting.
Services that fix this
Central AC Repair
Systems that will not start, will not cool, freeze up, short-cycle or leak water.
Central AC repair in Fountain Valley
HVAC Troubleshooting
Thermostat problems, short cycling, uneven rooms, noises and intermittent faults.
HVAC troubleshooting in Fountain ValleyThis guide is general information for homeowners, not a diagnosis of your system. For anything involving gas, carbon monoxide, electricity or active leaks, stop and call a qualified professional.
