AC keeps tripping the breaker

A breaker trips for two reasons. An overload is too much current for too long, and it takes minutes to trip. A short circuit or ground fault is a sudden surge, and it trips at once. The timing you noted tells the technician which one to look for.

Check which breaker is tripping. The outdoor unit and the furnace or air handler are on separate breakers, and a tripping air-handler breaker points to the blower motor or, on electric heat systems, the heat strips.

1. Dirty condenser coil or filter. The compressor runs hotter and pulls more current until the breaker gives up, usually in the afternoon.
2. Failing capacitor. Without a healthy capacitor the compressor draws heavy starting current for too long. See what a capacitor replacement involves.
3. Condenser fan motor. A fan that is slow or stopped lets pressure and current climb fast.
4. Loose or damaged wiring. Wires that have rubbed through, burned terminals at the contactor, or a loose lug at the breaker.
5. Weak or wrong breaker. Breakers wear out, and some were mismatched to the unit from the start.
6. Compressor. Windings shorted to each other or to ground trip the breaker instantly. A mechanically tight compressor trips it on start.

With the power off, the technician checks the compressor and fan motor windings for shorts to ground and measures winding resistance. They test the capacitor, inspect the contactor and every connection for heat damage, and compare the breaker and wire size with the ratings on the unit's data plate. If nothing is shorted, they start the system and measure starting and running current against the nameplate.

That sequence separates a cheap fix from an expensive one. A weak capacitor, a burned wire or a dirty coil are small repairs. A grounded compressor is the largest repair in the system.

Everything past the filter and the debris is electrical testing on live or charged equipment. This is one symptom where you should stop early and let a licensed pro find the fault.

If the compressor is shorted to ground, the realistic choices are a new compressor, a new outdoor unit or a new system. On an older system out of warranty, that repair often does not make financial sense. The compressor replacement cost guide covers how to judge it. For every other cause on the list, repair is the normal answer. The AC repair overview explains what a fair diagnosis and quote look like.