Light Switch Keeps Tripping the Breaker: Causes and Fixes

Short answer: When a breaker trips as you flip a light switch, the breaker is reacting to a fault on that circuit. A trip the instant you flip the switch usually means a short circuit in the switch, the box, the fixture or the wiring between them. A trip a few minutes later usually means the circuit is overloaded. If the breaker has a TEST button, it may be an AFCI or GFCI breaker reacting to arcing or a ground fault. Reset it once. If it trips again, leave it off and call an electrician: a short or an arc that keeps happening can damage the wiring.

What the timing of the trip tells you

The common causes

A short in the switch or the box. A wire that has worked loose from its screw, or insulation that has been nicked, can let the hot wire touch the ground wire or the metal box. The trip is instant and you may see a spark or hear a pop at the switch.

A faulty fixture or bulb socket. Worn sockets, cracked insulation inside the fixture, and failing LED drivers are common, especially in older fixtures and in fixtures that run hot. If the breaker stops tripping when you take out the bulbs, the fixture is the first suspect.

Damaged wiring. A nail or screw driven through a cable during a remodel, or wiring chewed by rodents in an attic, can create a short that only shows when that light is on.

Arcing that an AFCI breaker catches. Newer homes and remodeled rooms have AFCI breakers, which trip when they detect sparks from a loose connection or a worn switch. The trip can seem random. Our guide to GFCI, GFI and AFCI protection explains what these breakers detect.

Moisture. Outdoor lights, porch lights and bathroom fans with lights on GFCI-protected circuits can trip when water gets into the fixture or the box.

An overloaded circuit. If the trip comes after a delay, the light may be the last straw on a circuit that is already running space heaters, a window AC unit or kitchen appliances.

What you can safely check

1. Look at the breaker. If it has a TEST button, it is an AFCI or GFCI breaker. Note which kind; it helps the electrician.
2. Turn off and unplug other things on the same circuit, then reset the breaker once and try the light. If it holds, the circuit is likely overloaded.
3. Try it without the bulbs, with the breaker off while you remove them. If the trip stops, the bulbs or the fixture are the problem.
4. Check outdoor fixtures for water after rain, from the outside only.

Do not open the switch box or the fixture with the power on, and do not keep resetting a breaker that trips the moment you flip the switch. Each reset sends full fault current through whatever is shorting. In Rock Hill, the city requires electrical work in a home to be done by a licensed contractor.

When to call an electrician

Call us if the breaker trips the instant you flip the switch, if you saw a spark or smelled burning at the switch or fixture, if the switch or cover plate is warm, if an AFCI breaker keeps tripping, or if the checks above did not find the cause. If you were planning to replace the switch, our guide on how to change a light switch lists the signs that the problem is the wiring, not the switch.

We trace the fault, fix it at the source and test the circuit before we leave. We work across Rock Hill, Fort Mill, York County and Charlotte, and you get the price before any work starts.