Why an AC Keeps Tripping the Breaker

A circuit breaker has one job: to cut the power when a circuit draws more current than its wiring can safely carry. When the breaker for your air conditioner trips, it has detected exactly that. Understanding what makes an AC draw too much current explains why the rule for breakers is so strict, and why the fix is almost never at the panel.

What the breaker is protecting

The AC circuit is sized for the equipment on it. The compressor is the heaviest load in the house, and on start-up it briefly draws several times its running current. The breaker is chosen to tolerate that brief surge and to trip on anything larger or longer. When it trips, one of three things is happening: the compressor or a motor is drawing far more than it should, current is flowing somewhere it should not (a short or a ground fault), or the breaker itself has weakened with age.

Resetting sends full current back into whichever of those it is. If the cause is a compressor struggling to start, each reset heats its windings further. If the cause is a chafed wire, each reset heats the fault until the insulation fails completely. That is why the rule is one reset. Hold it, watch it, and if it trips again, leave it off and call. The breaker symptom guide says the same thing in fewer words, with the safe checks laid out.

The causes, roughly in order of likelihood

A failed or weak capacitor. The capacitor gives the compressor and fan their starting push. Without it, the motor tries to start on its own and draws a heavy, prolonged surge. The breaker trips at start-up, every time or on hot afternoons. The capacitor article explains the part in detail.

A compressor drawing too much current. Worn bearings, internal damage or a compressor that has been run with low refrigerant can draw excessive current even with a good capacitor. This is the expensive cause, and the one a technician rules in or out with a meter before replacing anything cheaper.

A dirty outdoor coil or blocked airflow. A coil that cannot shed heat pushes pressures up, and the compressor works harder and draws more. The breaker trips at the hottest hour of the day and holds in the morning. Cleaning the coil is a modest repair with a large effect.

A short or a ground fault. Insulation chewed by a rodent, a wire rubbed through by years of vibration, a loose lug at the contactor that has been heating up, or a motor whose windings have failed to ground. These trip the breaker instantly and often smell hot. This category is a fire risk, which is why nobody should be resetting a breaker to see whether it holds.

A weak or wrong breaker. Breakers do age and can trip below their rating. Occasionally someone has fitted a replacement with the wrong rating. A technician checks the rating against the equipment, but this is the least common cause and should be the last conclusion, not the first.

What you can safely do

Very little, on purpose. Reset once. Note when it trips: instantly at start-up, after a few minutes of running, or only on hot afternoons; each pattern points somewhere different. Look at the outdoor unit from a distance for a matted coil or debris. Check whether the panel or the breaker smells hot or looks discolored, and if it does, switch the main breaker off if you can do so safely and call. That is the complete list. There is no safe homeowner check inside the panel, inside the outdoor disconnect or inside the unit.

What you should never do

Never replace the breaker with a larger one. The breaker rating protects the wiring, and a larger breaker lets the wire overheat before anything trips. Never bypass, tape or hold a breaker in. Never open the outdoor unit to inspect the capacitor or contactor; the capacitor holds a charge with the power off. And never treat a second trip as a fluke.

How the technician finds it

The order matters, because some tests are unsafe with the power on. With the disconnect pulled, the technician inspects the contactor, capacitor, wiring and connections for heat damage, and tests the compressor and fan motor windings for shorts and ground faults with a meter. Only then does the power go back on, under supervision, with a clamp meter on the compressor to read what it draws on start and while running, compared with the rating on the equipment. The breaker rating and the wiring are checked, and the coil and airflow are inspected because an overheating system draws high current for cheap reasons.

You then hear the cause and the repair price before any work starts. A capacitor, a contactor, a cleaned coil or a repaired connection are routine. A compressor drawing excessive current on its own is explained honestly, with the options, so you decide with the facts. The pricing page explains how the diagnostic visit fee and the repair price are separated.

When it is an emergency

A breaker that trips twice is a call, not an emergency, as long as it stays off. It becomes an emergency when there is a burning smell, smoke, a hot panel or visible sparking. Switch the main off if it is safe, and use the emergency AC repair page; the phone is answered 24/7. If you noticed a smell before or during the trip, the burning smell guide explains which smells mean what.