GFCI seemed to fizzle and pop, and now works as a non-GFCI outlet - what happened?

Question

An outdoor GFCI that's under a covered porch has been working fine for a long time, but recently started failing to turn off when the 'test' button is hit. Here's what I observed.

Right after plugging something into the outdoor GFCI outlet, the GFCI and a light that gets power from it both turned off. I realized I may have accidentally hit the 'test' button on the GFCI while plugging this bulky plug in, which has happened before. I pressed reset and as expected, the light and outlet both got power back, but once power was back I could here an electric fizzling sound. I pressed reset again and firmer, and while depressed the power was off and when released the power and fizzling sound came back. I pressed test intentionally to see if that was working, and it did cut the power. Upon pressing reset a few moments after that, the power and fizzling sound came back, and then after a second or two a sudden pop and flash of blue from within the outlet, as if something arced. Power stayed on, and now when I press 'test' nothing happens and when I press 'reset' power is off when depressed and on when released. The outlet seems to function normal aside from 'test' not cutting power (and the test button itself appears half-depressed and not being fully released).

I'm wondering what could've happened, and what to watch out for if opening this up. Will simply replacing the GFCI be good enough, or should other follow up measures be taken to ensure safe functioning?

Answer 1

What happened?

1. Turns out, "outdoor leak-proof covers" don't actually work.
2. The GFCI was destroyed by the weather.
3. Your pressing "test" exposed the weather damage, and finished the beast off.
4. The noticeable arcing after you reset was grim warning of imminent hazard. Your healthy fear of electrical things should've kicked in; it certainly would have mine!
5. You tinkered with it instead; this ultimately welded the contact closed.

You now have a GFC. Ground Fault Circuit (absolutely nothing).

The quick fix is to replace this GFC with an outdoor-rated GFCI+receptacle. You'll be doing this again though.

The good fix is don't leave valuable electronics outside. Follow this circuit back inside the building, and find the next receptacle on this circuit that's closer to the supply. Follow the circuit from receptacle to receptacle until you find one that's in the nice dry indoors. Fit a GFCI+receptacle there, test it, then feed the rest of the circuit off its LOAD terminals. Replace this GFC with a plain receptacle.

Answer 2

My answer assumes you've determined that the appliance you plugged into the gfci was not the culprit to begin with. When you replace the gfci, it would be interesting to break it open and see if you can detect what happened inside.

GFCI's do have an expected lifecycle, like everything else, and do go bad from time to time. It is a good idea to check them monthly, at least, and make sure they are still functioning properly. If the outlet gets a lot of usage and vibration, the terminals may have loosened up on the wires, hence the spark you saw; or, something else simply burned out inside the device.

I wouldn't expect you to have any other issues if you saw the spark inside the gfci. To be safe, turn the circuit off before removing the cover. Ensure power is off by checking for voltage. I would look for burned marks on the device to cue you in to the cause, possibly around the terminal screws, which might indicate a loose connection. Also, does the wiring look bad in the outlet box (burned, blackened)? Make sure your wiring in the box isn't cracked or burned apart from the event or from slow overheating.

With the breaker still off, and once the gfci is removed you may want to perform further tests. Make sure everything is removed from the circuit (unplug everything on that branch circuit), then test the wiring at the box to make sure there is no continuity between neutral and hot, and grounding and hot. If you have access to a megohmmeter, doing a similar test to the above-described with 1000vDC voltage would show if the insulation is still good on the wiring throughout the circuit, however you should also disconnect the hot wire from its breaker or fuse in the panel and cap it before you begin. This would be mostly for peace of mind, because I think you are probably going to be okay simply replacing the gfci and continuing to monitor it once a month.