Most common causes
- Dirty filter or outdoor coil. When airflow is poor or the outdoor coil is caked with dirt, the system works harder and draws more current.
- Failing capacitor. A weak capacitor makes the compressor or fan motor struggle to start, which pulls high current and can trip the breaker.
- Shorted or grounded motor. A fan motor or blower motor with damaged windings can short out and trip the breaker right away.
- Compressor problem. A compressor that is failing or has a short to ground will trip the breaker at startup. This needs testing by a technician.
- Damaged wiring. Rodents, age, or heat can damage wiring at the outdoor unit or air handler and cause a short.
- Worn or wrong breaker. Breakers can weaken over time. A breaker that is the wrong size for the unit can also trip. Only a qualified technician or electrician should check this.
What you can safely check
- Turn the system off at the thermostat before resetting anything.
- Find the tripped AC or air handler breaker in the main panel and reset it once. Do not open the panel cover.
- Wait 5 to 10 minutes, then turn the AC back on.
- If it trips again, leave the breaker off and do not reset it again.
- Replace the air filter and clear debris from around the outdoor unit.
- If you smell burning or see scorch marks near the unit, turn it off and do not use it until it is checked.
Call a technician if
- The breaker trips a second time
- The breaker trips the moment the AC starts
- You smell burning or see scorch marks
- The outdoor unit buzzes or hums before the breaker trips
- The breaker feels hot or the panel makes noise
What affects the repair cost
If it was a one time trip from a dirty filter, the fix may cost nothing more than a filter. A capacitor or contactor is a moderate electrical repair. Motor replacement depends on the motor type. A shorted compressor is the most serious case and on an older system often leads to a repair versus replacement conversation.
