AC Tripping the Breaker in Hillsborough

AC Tripping the Breaker in Hillsborough

An AC that trips the breaker is the system protecting itself from a part that is pulling too many amps. The compressor or fan motor draws a hard inrush at startup, and if a capacitor is weak, a motor bearing is seized, or the wiring has shorted, the current spikes past what the breaker will hold and it cuts power. That is the breaker doing its job. The fix is finding which part is drawing too much, not buying a bigger breaker.

Cooling load is moderate in Hillsborough. The town sits high enough and shaded enough that summers stay mild, so these systems do not run flat-out the way an inland unit does. That works in your favor. The failures we see are usually a single aging component on one of several condensers, not a compressor cooked from heavy use. Because most of these estates carry more than one system, the unit that trips is the one to test, and the others usually keep the house comfortable while we work.

It is almost always one fixable part. A failed run capacitor will trip a breaker. So will a pitted contactor or a condenser fan motor with a dragging bearing. Each is a same-visit repair, and we measure the actual amp draw to tell them apart before we quote anything.

Common causes

Failed run capacitor. A weak capacitor makes the compressor or fan motor strain to start, and the amp draw climbs until the breaker trips. We test capacitance with a meter against the rating stamped on the can. A capacitor reading well below spec gets replaced on the spot, and it is the most common cause we find.

Shorted or grounded compressor windings. When compressor windings break down and short to the case, the unit draws a dead-short level of current the instant it tries to start. We isolate the compressor and ohm the windings to ground. A grounded compressor is a real failure, and on a multi-system estate we tell you whether replacing that one compressor or the condenser makes more sense.

Pitted or welded contactor. The contactor is the relay that powers the outdoor unit. When its contacts pit and stick, current arcs and can spike past the breaker. We inspect the contacts and measure the draw across them. A burnt contactor is an inexpensive part and a quick swap.

Locked or dragging condenser fan motor. If the outdoor fan bearing seizes, the motor stalls and pulls locked-rotor amps until the breaker opens. We check that the fan spins freely and read the motor's running amps against the nameplate. A dragging motor gets replaced before it takes the compressor down with it from high head pressure.

Dirty condenser coil raising head pressure. On the wooded Hillsborough lots, leaf litter and pollen pack the outdoor coil. A clogged coil traps heat, head pressure rises, and the compressor works harder and draws more amps until it trips mid-cycle. We read pressures and amps, then clean the coil and confirm the draw drops back into range.

Shorted or chafed wiring. Wiring that has rubbed through its insulation against a cabinet edge or been chewed will short and trip instantly. We inspect the disconnect, the whip, and the low-voltage runs for damage. Repairing the short is the fix; it is not a part replacement.

How we diagnose it

• Confirm which of the home's systems is tripping and reset once under a clamp meter to read the actual amp draw at the moment it cuts out.
• Test the run capacitor against its stamped rating and inspect the contactor for pitting.
• Ohm the compressor windings to ground to rule in or out a shorted compressor before condemning anything.
• Spin the condenser fan by hand and read its running amps to catch a seizing motor.
• Inspect the disconnect, whip, and low-voltage wiring for shorts, and check that the breaker size matches the unit's nameplate rating.

$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.

AC Tripping the Breaker in Hillsborough: common questions

Nearby and related

AC Tripping the Breaker near Hillsborough: Menlo Park · Palo Alto .

This is usually a ac repair in Hillsborough job. See our ac repair overview or the Hillsborough service area.