Exterior GCFI outlet tripping. No moisture detected at the outlet. What diagnostic steps should I take before I change the outlet?

Submitted by MartyAtThePoonTower t3_z8crbu in DIY

Put up Christmas lights this weekend. The exterior GCFI outlet on the side of the house continually trips (at the outlet, not the breaker). Sometimes a minute after the lights are on, sometimes it takes 20 minutes to trip and I've had intervals anywhere in between. I have additional xmas lights connected to one other exterior outlet on the same circuit. No issues with it.

The outlet is in a box with a cover. I can't detect any moisture in or around the box, or on the backside (unfinished basement). Lived in this house for 7 years now, no heavier load on the circuit than I've had before with no problems.

Before I go replace the outlet, what other diagnostic steps should I take?

Edit for Update: RESOLVED. Moved the entire line to the outlet I knew was good. It tripped out immediately. Replaced the decoration circuit a piece at a time and located the culprit - a flood light whose rubber gasket apparently got crimped and pushed off while it was in storage. Again, thanks to all who posted.

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trapperjohn3400 t1_iyazap9 wrote

I'm going to suggest that it may actually be the lights tripping it. Try a large load (like a space heater or a shop vac, ect.) and see if that trips it. You might have moisture where the lights connect into the other lights potentially causing issues also.

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SuzieQbert t1_iyaznpm wrote

^^^ Definitely give this a go. For sure sounds like a problem with your lights .

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Parkje04 t1_iyb1fk2 wrote

+1 to this theory. This exact scenario happened to me last year. I replaced the GFCI and the outdoor outlet before realizing the problem was the lights themselves. Could be one of the strands are getting moisture in them, or some other issue related to the lights.

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ZipperJJ t1_iyb5oj7 wrote

Same here. When I first did lights they were incandescent and they were too much of a load for my one plug. I replaced them with LED and it stopped tripping.

Then one year it was really wet and I started getting tripping again. My LED strings were too wet so I got some of those waterproof outdoor plug covers to put the plugs in. Haven’t had a problem since.

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bluecar92 t1_iyb1ymc wrote

Yup, same thing happened with me one year. One of the connections between a string of lights and an extension cord was wet.

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5degreenegativerake t1_iyb6jgl wrote

GFI outlets don’t trip based on moisture, they trip on a difference in the current between the line and neutral. The most likely cause is a bad bulb, or bad socket on the lights that is leaking current to ground and causing the trip. Obviously moisture can also cause current leaking to ground, but moisture is not a requirement to have “nuisance” tripping.

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jawshoeaw t1_iybxc7t wrote

I have lots of lights that are soaking wet for the month of December and they don’t ever trip my gfci. It’s weird honestly. In my experience gfci just go bad and it’s easier to replace them after some basic troubleshooting.

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michaelpaoli t1_iybymyi wrote

>GFI outlets don’t trip based on moisture, they trip on a difference in the current between the line and neutral.

Get enough moisture between hot/line and ground, and you'll have that difference in current that'll trip the GFCI. That principle may also save someone's life - e.g. wet feet in bathtub, hand on faulty device plugged in that contacts or leaks hot to the person's hand, flows through them, into feet in tub and ground ... again, moisture, current imbalance between line/hot and neutral ... and ... it trips.

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ccarr313 t1_iyc7qgw wrote

They also trip if you pull too many amps. Which can be caused by a short due to moisture, in whatever is plugged in or the socket.

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user47079 t1_iyazhay wrote

Try plugging in something else that is known good, the lights may have developed an issue (could be a rusty wire arcing or other intermittent failure). If the other thing works fine, it's the lights. If the GFCI still trips, replace it.

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Photodan24 t1_iycz8q1 wrote

Sound troubleshooting here. Divide and conquer.

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Guygan t1_iyaykbc wrote

Outlets are cheap. Replacing it is Step One.

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ntourloukis t1_iybgz5m wrote

I disagree.

I may be wrong, but it seems like he’s confused about how a gfci works and is only checking for moisture at the outlet itself. He also hasn’t mentioned trying any other load besides the one set of lights.

So OP, if you’re reading here, unless more than one set of Christmas lights causes this trip, you probably have moisture getting into your lights somewhere. Could be the female side of the lights, could be a loose or broken bulb.

If a few different loads all trip it, then definitely change the outlet.

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cplog991 t1_iyayux9 wrote

Unhook half your lights and see if it still trips

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therealdarkcirc t1_iyaylqp wrote

GFCI outlets generally expire after 10 years. They can also fail. I'd replace it first.

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Emergency-Wave-5335 t1_iybsn91 wrote

This statement has no basis in fact. Some GFI outlets fail in a year, some are fine after 30.

This is a problem with the lights, not the outlet.

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michaelpaoli t1_iybz0xr wrote

>This is a problem with the lights, not the outlet

Could be either at this point - insufficient data to conclusively determine.

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Dirtzoo t1_iybjpqe wrote

They go bad

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Pjtruslow t1_iyb9h1p wrote

I have also seen GFCI outlets fail outright. They’re somewhat expensive but may be worth the cost in exchange for the headache.

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03223 t1_iyb149d wrote

If you have an extension cord that will reach, try plugging string A into outlet B, and vice versa. See if problem follows lights or outlet. Are these LED lights? I installed an LED fixture in my garage and it would trip the GFI.. had to take it out. Never figured out issue.or some reason

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LarixOcc t1_iyb0fop wrote

I had an unused bollard yard light that was corroded down the line from a GFCI. It was 20ft away but wired in.

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Raul_McCai t1_iyb1zvb wrote

run a cord from another GFCI outlet and see if they trip that one too, If so it's the lights

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meowmeowroar t1_iyb8mzj wrote

Ours started tripping because a lizard crawled inside and died lol. No new outlet needed just had to be opened and removed…. I love Florida

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michaelpaoli t1_iybz88u wrote

Ants killed two GFCI outlets where I live. The buggers like the tiny extra little bit of heat the electronics in there generated under load ... that was all fine until the ants got a bit too cozy and dense across 120 VAC.

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Mildly_Angry_Biscuit t1_iybbkv8 wrote

If it were a newer GFCI then I'd start suggesting troubleshooting. If its anything older than 5 years and an outdoor GFCI, I strongly recommend replacing it as a matter of course, because they do have a finite lifespan and that lifespan is shortened with exposure.

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Macsmackin92 t1_iyb0vkp wrote

Check to see if the wiring is correct. My garage plugs were constantly tripping. Had an electrician check it out and one outlet was wired backwards.

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woodmanalejandro t1_iybavgv wrote

they make waterproof housings for where you connect strands of lights together, I’d give those a shot

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excunarder t1_iybes2n wrote

My gfic are connected to by bathroom gfic. (Don’t know if should be) but if 1 trips they all trip. I just press the button to reset

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mossywill t1_iybt8ac wrote

Just tonight my outdoor Christmas lights tripped the breaker and it was caused by the way I had multiple strands plugged into each other. I put them in a 3 outlet set up so they wouldn’t have to be plugged in together and it stopped tripping. Good luck figuring it out. I felt like Clark W. Griswold.

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michaelpaoli t1_iybybuc wrote

Try a fairly heavy load that's compact and highly well insulated from ground - just hot and neutral and well insulated with nothing for it to leak off to anywhere nearby. If it still trips the GFCI outlet, you probably have a faulty GFCI outlet. Various intrusions can cause them to fail, e.g. moisture, ants(!), ... also possible, though less likely, that the GFCI circuit itself might be faulty, or there could be some wiring issue that's causing it to trip (e.g. by causing excess heat build-up from poor connections or faulty components).

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thebluelunarmonkey t1_iybzvwo wrote

I think the GFCI is working properly, esp since you said you had no problems before with other equipment plugged in.
A long string of christmas lights, CHEAPLY MADE, has dozens of open air exposure to the conductors, place these exposures next to your home, add moisture from the air, you have a tripping GFCI. Wrapping lights around a tree would be especially prone to trip a GFCI.

Connect your lights to a non GFCI outlet using an extension cord. You're not going to be touching the lights while they are plugged in, anyway.

Unless you've already stapled the lights in place, you can put the string of lights in a plastic garbage bag, the GFCI should no longer trip. Indicating your lights are the problem, not the outlet.

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WeeklyHeretic t1_iyc054p wrote

As others have suggested, it only takes a 10 minutes to plug in a hair dryer or space heater to the suspect outlet and see if it holds. If the GFCI is bad, it will likely trip pretty quickly. If it runs a hair dryer for 10 minutes, the issue is in your lighting and the GFCI is just doing its job. GFCI outlets work by detecting leakage current to ground. It doesn't take much current leaking to trip one (4-6mA). They can trip with even tiny loads attached to them if that load has some leakage current to ground. The other good suggestion was to run an extension cord from another GFCI to your christmas lights and see if it trips too. Based on what happens, you can swap the outlet or not.

If it turns out your outlet is good, then look for any place your lights might be grounding out. Most christmas lights don't have a ground wire so they would need to ground to something in order to trip your GFCI. If it was a bare wire short, your light string would burn up like a fuse so it's likely a crimped wire with the insulation being crushed by something metal or something wet. A high-resistance short to ground will trip a GFCI but not trip the breaker behind it. The comments about moisture are right on as well since water can break down insulation and allow current to pass through it.

I've got outdoor GFCI outlets that are 20 years old and still function perfectly. One of them saved my life about 6 years ago when I stepped in a puddle that had a cord in it just as it tripped out. Assuming the GFCI is the problem ignores the fact it could be doing exactly what it was designed to do. Stay safe.

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GetCookin t1_iyc37mq wrote

I’ll note the small possibility the outlet is wired wrong down the line as well. All the GFCIs in my house were intertwined circuit wise and would trip when another device would run down the line. Had to run an extra neutral line in one case. The random timing leads me to believe it could take OP that time to run something else on the circuit. Hoped it’s the lights. But you never know.

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spizzywinktom t1_iycu0w6 wrote

Your GFCI outlet is tripping because the C and F are mixed up.

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NotObviouslyARobot t1_iycwwle wrote

Sometimes builders cheap out on GFCIs, even when exterior. I found interior grade GFCIs on a million-dollar 7000 sf neo-plantation house. GFCIs also can wear out due to time, and corrosion, but there are some other good suggestions in the thread

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MartyAtThePoonTower OP t1_iydjwtp wrote

Huge thanks to everyone who posted. This sub is awesome. Based on what I’ve been advised here, I’m going to plug the lights in the GCFI outlet that I know is working properly. If that trips, I know the issue is somewhere in the lines and I’ll eliminate and recheck until I locate it.

If it does not trip, I’m going to plug a hair dryer into the suspect gcfi and see if that trips. If it does I’ll proceed to replacing the outlet.

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