Total no-response from the AC — outdoor unit silent, indoor blower silent, thermostat may be dead too — is usually a power issue. The system isn't broken so much as cut off. Run through this checklist before you call.
Most Likely Causes
1. Tripped breaker
Most central AC systems have TWO breakers: one for the outdoor condenser (large double-pole) and one for the indoor air handler (single-pole). Check both. Reset by flipping fully off then back on.
2. Blown disconnect fuse
The metal box mounted near the outdoor unit holds a pull-out disconnect that may have blown fuses. Pull it out — if you see two cylindrical fuses, they may be bad.
3. Tripped float switch
Condensate backup → float switch trips → kills power to the thermostat → AC won't engage. Look for a clogged drain pan.
4. Blown low-voltage fuse on control board
Small 3 or 5 amp fuse on the air handler control board. Blown by a shorted thermostat wire (often rodent damage). Cheap fix once you find it.
5. Dead thermostat
Batteries dead, or the thermostat itself failed. Pull the cover and check.
6. Failed contactor in outdoor unit
If the indoor blower runs but the outdoor unit is silent, the contactor may have failed open. Common after a power surge or 10+ years of cycling.
Try These Steps Before You Call
- Check the breaker panel — flip both AC breakers fully off then back on.
- Check the outdoor disconnect — pull out the handle, inspect for blown fuses.
- Check the thermostat — replace batteries if applicable.
- Check for water in the condensate pan or a tripped float switch.
- If the indoor blower runs but the outdoor unit doesn't, you likely have a contactor or capacitor problem at the outdoor unit.
Still not working?
If breakers + thermostat + drain look fine, the problem is component-level. Call (214) 466-6465.
Call (214) 466-6465