Why Does My AC Keep Tripping the Circuit Breaker?

A tripped breaker is your electrical panel doing exactly what it's built to do: cutting power before a circuit draws enough current to overheat. So when your AC keeps tripping the breaker, the breaker usually isn't the villain. It's the messenger. Something in the system is pulling too much power, and the breaker is shutting it down before that turns into a bigger problem.

The tricky part is that a lot of different failures show up as the same symptom. Below are the usual causes, from the simple to the serious, plus what you can safely check yourself and where you need to stop and call. First, the one rule that matters most.

Start With the Easy Stuff

Before assuming the worst, rule out the cheap causes. These are the ones you can check without any tools.

A dirty filter or coil. When airflow is choked by a clogged filter or a filthy outdoor coil, the system works harder and pulls more current to do the same job. Sometimes that's enough to nudge it over the breaker's limit. Swap the filter and, if the outdoor unit looks dirty, give it a rinse. We walk through that in our guide to cleaning the condenser.

A frozen unit. If the system iced over and you kept running it, the strain can trip the breaker. Let it fully thaw before doing anything else. Our frozen coil post covers why this happens.

If a fresh filter and a clean, thawed unit fix it, great. If the breaker trips again after that, the cause is electrical or mechanical, and that's where a technician comes in.

The Electrical Causes

Most repeat-tripping comes down to a part in the system drawing more current than it should. These aren't DIY fixes, but knowing what they are helps you understand the diagnosis.

• A failing capacitor. The capacitor gives the compressor and fan motors the jolt they need to start. As it weakens, the motors strain to start up and pull extra current. It's one of the most common causes we find, and one of the least expensive to fix.
• A worn contactor. The contactor is the switch that sends power to the outdoor unit. Pitted or stuck contacts cause erratic current draw and trips.
• Loose or corroded wiring. Connections loosen and terminals corrode over time. A bad connection creates resistance and heat, and that can trip the breaker or, worse, start a fire. This is exactly what an annual tune-up is meant to catch.
• A grounded or failing compressor. This is the serious one. When a compressor's internal windings break down, it can short to ground and trip the breaker instantly. A grounded compressor is often the end of the road for that unit.

When the Breaker Itself Is the Problem

Once in a while, the AC is fine and the breaker is the weak link. Breakers wear out, and after enough years of tripping they can get "soft" and trip at lower and lower loads. A breaker that's undersized for the unit, or one that shares a circuit it shouldn't, can also trip under normal operation.

This is a real possibility, but it's the last thing to assume, not the first. Blaming the breaker and simply swapping it for a bigger one is dangerous. If the wiring isn't rated for the higher amperage, you've removed the safety device that was protecting your house. A tech confirms the breaker is actually bad and correctly sized before touching it.

Why It Always Seems to Happen in a Heat Wave

There's a reason these calls cluster on the hottest days. When it's 90-plus outside, the AC runs longer and the compressor works at its hardest, which pushes current draw to its peak. A capacitor that was limping along, a connection that was marginally loose, or a coil that was borderline dirty finally tips over the edge under that load.

That's also why a spring AC tune-up prevents so many of these. When we check the capacitor, tighten the electrical connections, clean the coil, and verify the refrigerant charge before summer, the weak spots get caught while it's cool out instead of failing on the Fourth of July.

What to Do Right Now

If your AC is tripping the breaker, here's the order of operations:

1. Reset it one time. If it holds, keep an eye on it.
2. If it trips again, leave it off. Don't keep resetting it.
3. Change the filter and check that the outdoor unit is clean and not iced up.
4. If it still trips, call for AC repair. Since the causes range from a cheap capacitor to a failed compressor, a proper diagnosis is the only way to know what you're dealing with, and on an older unit it also tells you whether a repair or replacement makes more sense.