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We had a storm last night (lightning/wind/rain) and this morning the dead front GFCI switch (located in garage) for all the exterior outlets was tripped. The LED is on so the switch is getting power. At first the light was solid red, indicating a fault. I tried resetting it and it immediately trips again. The trip sound seems a bit more like a "pop" than I remember, but this could just be me. After this the light was blinking red. Not sure if that means something different or if its just blinks on a timer then goes solid. So I unplugged everything from the exterior outlets, tried again and it still immediately trips. House is 2 years old, and have not had any electrical problems so far, so I'm hoping this isn't internal wiring.

Hardware store is 30m away so I want to diagnose as much as possible before leaving and buying stuff I don't need.

From my limited experience it seems like this could be...

  1. Bad GFCI switch
  2. Bad exterior outlet causing a short
  3. Something worse

How can I go about testing the exterior outlets with the power off? Would a receptacle tester be able to detect a short with no power? (The prongs of my multimeter unfortuntely wont fit into an outlet, so I may have to get a new device)

I've added and replaced outlets before so I'm comfortable doing the work, I'm just trying to plan out the most efficient way to find the root cause.

Update: Wanted to mention that the circuit has an in-ground electric dog fence and a OTA antenna amplifier on it, which are obvious ways for lightning related surges to enter the system.

Update: The problem was a failed/fried GFCI dead-font switch. My guess is that a surge related to the lightning fried that switch. Following the accepted answers test procedure identified that as the culprit prior to having to open any of the outlets on the circuit. Replaced that switch and all is good.

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    0. GFCI working as intended, protecting you from a ground fault on the exterior outlet circuit, probably related to water intrusion (especially if it gets better by itself as things dry out.) I mean, the things do fail, and are subject to power surge damage, but the first thought really should be "probably a ground fault" not "must be broken", and that's not "3." Arguably not 2, either (a short would be tripping the breaker. A ground fault can be a whole lot less than a dead short.) To make any guess at "blinking red" we'd need to know the exact GFCI deadfront switch you have.
    – Ecnerwal
    Sep 13, 2022 at 12:45
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    Good idea to let things dry out and see if the problem remains. If during the storm there was lightning involved you may have had a power surge which fried the GFCIs. we here at SE had that discussion a few days ago. It's not uncommon for a power surge to fry GFCIs. Ecnerwal's diagnostic approach is spot on. Sep 13, 2022 at 13:18
  • @GeorgeAnderson yes there was a ton of lightning, which is why my first thought was it being fried. We've had 2+ inch rain/wind storms this month without lightning and everything held up fine, which is why water intrusion was not really on my list. It's still certainly possible. If things resolve after drying up today then I'll know that was it. Sep 13, 2022 at 14:48
  • @GeorgeAnderson Forgot to mention - this exterior circuit has an in-ground electric dog fence and a OTA TV antenna amplifier plugged into it. So both of those are excellent ways for weather related power surges to get into the circuit. A direct strike is pretty much out of the question because there is no burn damage, but a surge is def possible. Sep 13, 2022 at 15:00
  • It doesn't need to be a direct strike. Lightning creates immensely powerful electromagnetic fields which creates power surges via induction that travels via the distribution system. That it's an outside outlet with the devices you mentioned plugged in. ....pretty likely it's fried. Sep 13, 2022 at 16:34

1 Answer 1

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Turn off the circuit breaker, open up the deadfront/switch GFCI, remove (only) the load wires, turn breaker back on, see if it resets. If so, it's not the GFCI. If not, it probably is.

If not the GFCI, you then turn off the circuit breaker again, and open the first outlet after the GFCI (if you know the layout of the circuit - otherwise it becomes more random, but physically close is a good guess usually) and remove and insulate one set of wires (since it's normally going to have a set in and a set out.) Breaker back on, see if the GFCI will reset, check for power at that outlet. If the GFCI resets, but the outlet has no power, breaker off, reconnect the first set of wires, disconnect/isolate the second set of wires, try again.

Lather, rinse, repeat until you find a set of wires that prevents the GFCI from resetting - your ground fault is there, or at the far end of that set of wires. One in 10,000 times it's along that set of wires (or higher chance if you've recently had people driving nails willy-nilly into the walls.)

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    I would suggest that you add step 0 (from your comment) of "Wait until everything dries out", since there may have been water infiltration into one of the outdoor outlets causing the problem. OTOH, doing it while things are still damp may help identify which one is wet and allow addressing the (possibly damaged) in use cover.
    – FreeMan
    Sep 13, 2022 at 13:03
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    If looking for the problem to solve it, strike while the outlet may still be wet enough to cause the problem. If not in urgent need of the outside outlets TODAY, let them dry out and see if the problem goes away, then go hunting NEXT time it happens.
    – Ecnerwal
    Sep 13, 2022 at 13:11
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    @TheShoeShiner Nope. Wires connect all the outlets. If you don't disconnect the wires, the fault will show up on any outlet you test. While you can try to localize it by the resistance value, odds are that the margin of error in the reading is greater than the wire resistance between parts of the circuit. Opening them up also lets you say: "hmm, this one is full of water, could be our problem" and take corrective action.
    – Ecnerwal
    Sep 13, 2022 at 14:30
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    Expanding on what Gil mentioned, a faster way to troubleshoot any type of problem is to break the problem area in half and then half again... In this example, if you have 8 outlets on a GFCI for example, disconnect the last 4 and test. Now you know which 4 fails the test. Next you disconnect 2 of the 4 that fail the test and then you only have to test 2. You might have two issues causing both sets to fail, but in most cases this will more quickly get you to the problem when the problem area is larger. Sep 13, 2022 at 21:49
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    @TheShoeShiner You don't have to check every outlet. Just make an educated guess as to the sequence of the string, and break the string at the halfway point. Test again. Now you know which side has the fault. Divide it in half again. In an 8-socket string, you find it in 3 tries. Sep 14, 2022 at 1:30

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