An air conditioner or heat pump that trips its breaker is drawing more current than the circuit allows, and the usual reasons are a weak or failed capacitor (the compressor or fan motor struggles to start and pulls high amps), a dirty outdoor coil or blocked airflow (the compressor works harder and hotter), a failing compressor or fan motor, a short in the wiring or a contactor, or, less often, a breaker that’s worn or undersized; reset it once, and if it trips again leave it off and call, because repeated resets risk fire and can destroy the compressor.
Right now
Turn the thermostat to Off. Reset the breaker once. Set the thermostat back to Cool. If the breaker holds, watch it through a cycle or two and do the checks below. If it trips again immediately or within minutes, leave it off and book a technician. Don’t tape it, don’t replace it with a bigger breaker, and don’t keep resetting it.
Which breaker?
Outdoor unit (condenser/heat pump) breaker: usually the compressor, fan motor, capacitor, contactor or the outdoor wiring. Air handler / furnace breaker: blower motor, heat strips (a failed strip element or sequencer is a common cause of an air handler breaker tripping in winter), a shorted transformer, or wiring. Note which one trips.
Check first (power off at the breaker)
Outdoor coil clean and unobstructed? Filter clean? Any sign of scorching, melted insulation, or a burning smell at the disconnect or unit? Insects (ants and lizards) inside contactors cause shorts more often than you’d think. If you see burnt wiring, don’t restore power; call.
Likely causes, ranked
| Cause | Sign | Who fixes it | Typical cost |
|---|---|---|---|
| Weak/failed capacitor | Hard starts, hum, trips at startup | Technician | $130–$400 |
| Dirty coil / restricted airflow | Trips on hot afternoons | You / technician | $0–$400 |
| Failing compressor (high amps, grounded windings) | Trips instantly at start; loud hum | Technician; often replace | $1,100–$4,650 |
| Fan motor failing | Fan slow/hot; trips | Technician | $350–$800 |
| Contactor or wiring short | Trips instantly; scorching | Technician / electrician | $150–$500 |
| Heat strip / sequencer fault (air handler) | Trips in heating mode | Technician | $200–$600 |
| Weak or undersized breaker | Trips with normal amps | Electrician | $150–$400 |
| Refrigerant overcharge or restriction | High head pressure, high amps | Technician | $200–$800 |
Costs from the repair cost guide.
When to call
If it trips a second time; if there’s any burning smell, scorching or melted plastic; if the outdoor unit hums loudly and won’t start; or if the trip is on the air handler in winter. A technician will measure compressor and fan amp draw against the data plate, test the capacitor and contactor, and check the wiring; ask for the readings. If the AC is also not cooling, start there. Electrical smells or smoke are an emergency. Every contractor on the North Carolina registry shows the license status we found.