Why does my GFCI outlet keep tripping?

A GFCI trips when it senses current leaking to ground, about 5 milliamps. When it trips again and again, it’s doing its job: something on that circuit is leaking. The usual culprits are moisture in the outlet box, a faulty appliance plugged into the circuit, or a GFCI worn out past 10 years.

What does it mean when a GFCI keeps tripping?

A tripping GFCI is not malfunctioning. It’s reporting a problem. The device watches the current going out on the hot wire and the current coming back on the neutral. When the two don’t match, electricity is escaping somewhere it shouldn’t, and the GFCI cuts power.

The threshold is small. A GFCI trips when the difference reaches about 5 milliamps. That’s a deliberately low bar, set well below the current that can hurt someone, so the power cuts before a shock turns dangerous.

OSHA describes a GFCI as a device

designed to shut off electric power in the event of a ground-fault within as little as 1/40 of a second.

So a GFCI that keeps tripping is catching a real leak, every time, in a fraction of a second. The job isn’t to make it stop tripping. The job is to find what’s leaking. Three causes cover almost every case: water, a bad appliance, or a worn-out device.

How do I find what’s tripping it?

Work the circuit, not the outlet. Most nuisance trips get solved in ten minutes by isolating what’s on the line.

Start by unplugging everything the GFCI feeds, including outlets downstream. A single GFCI can protect a string of plain outlets wired to its LOAD terminals, so the lamp in the next room may sit on the same protected circuit. Reset the GFCI with nothing plugged in.

If it holds, the fault is in something you unplugged. Plug devices back one at a time, give each a few minutes (a fridge or freezer needs a full cycle, including the defrost heater), and wait for the trip. The device that drops it is the one with the ground fault.

If it trips with everything unplugged and the box is dry, the problem is in the wiring or the GFCI itself, not in anything you plugged in.

Why does it trip after rain or in a damp garage?

Water is the most common reason a GFCI trips for no obvious cause. It takes only a little moisture bridging a connection to leak the 5 milliamps that drops the device.

Outdoor outlets are the usual offender. After a hard rain, water gets past a cracked cover or a gasket that no longer seals, pools in the box, and creates a leakage path. The outlet may work fine once it dries out, then trip again with the next storm.

Garages and unfinished basements do the same thing from condensation and damp concrete. A receptacle low on a garage wall, near a floor drain, or behind a chest freezer collects moisture over time.

Dry the box completely before resetting. Pop the cover, let it air out (a day in dry weather, longer if it’s humid), and check the gasket and cover for cracks. A weatherproof “in-use” bubble cover, $10 to $20, keeps an outdoor outlet sealed while a cord is plugged in and stops most rain-related trips.

Why does it trip when the fridge or freezer runs?

Refrigerators and freezers are the classic intermittent tripper, and the reason is built into how they run. The defrost cycle heats the coils to melt frost, which puts water right next to electrical connections. Over years, that moisture works into terminal blocks and wiring and starts leaking a few milliamps to ground, usually only during defrost. That’s why the trip seems random: it tracks the defrost timer, not anything you did.

Aging motors add to it. A compressor or fan motor with worn insulation leaks a little current, and the brief electrical kick when a motor shuts off can nudge a sensitive GFCI over its threshold.

This runs straight into current code. The 2020 National Electrical Code (210.8) expanded GFCI protection to cover garages, basements, and the outlets that serve refrigerators and freezers. A lot of fridges now sit on a GFCI for the first time and trip where the old unprotected outlet never did. The code is right; the appliance is the thing leaking. If a fridge trips a fresh, dry GFCI on a clean circuit, the fridge needs service, not the outlet.

When is the GFCI itself the problem?

Sometimes the device is just worn out. A GFCI has electronics inside that degrade, and an old one starts tripping on its own or refuses to hold a reset.

Suspect the device when it trips with everything unplugged and the box bone dry, or when it fails the monthly GFCI test: you press TEST and nothing cuts, or you press RESET and it won’t stay set. InterNACHI puts a GFCI’s service life at 15 to 25 years, and outdoor and bathroom units run toward the short end because of humidity.

A replacement is a $15 to $30 part and about 20 minutes with the breaker off. If you’re not comfortable working inside an outlet box, it’s a small job for an electrician. A dead or flaky GFCI in a bathroom, kitchen, or garage is unprotected wiring in the exact spot where water and electricity meet, so it’s worth fixing rather than living with a circuit you keep resetting.

A note from Kempt

A GFCI that trips once and resets is fine. One that trips over and over is a small mystery: a wet box, a bad appliance, or a device near the end of its life. Kempt keeps the map that solves it fast. Which outlets each GFCI protects, how old the device is, and whether the last few trips lined up with a storm or a defrost cycle. So instead of crawling behind the freezer with a flashlight, you start with the likely cause.