I've been searching these boards for 3 days straight and I still can't find an answer.. And I'm about to pull my hair out!

I have a small half bathroom in my basement, toilet and small sink. Over the sink is a medicine style mirror with a 17" florescent light fixture over it. This past weekend the GFCI outlet, which feeds the light, tripped for reasons unknown to me. I naturally hit the test button 16 times with no success. So I killed the power and opened the wall box, switch box, and light fixture. It was set-up to protect the downstream devices (line AND load). I replaced the outlet and that didn't help so I pig-tailed everything together and attached everything to the line terminal and that brought everything back to normal.

However, I don't want to just leave it as is because there obviously is a problem. Without tearing the wall paneling off, I think the setup is: Source>GFCI>switch>light.... I pulled all wires off the devices and tested for power and GFCI line black wire was the only hot one...

Thank you in advance!

  • Have you tried unplugging the down stream loads? It is possible there is a small leakage current developing and that is the cause. the florescent ballast could also be the problem. The last thing I can think of would be a loose conductor on the feed side some GFCI's will trip with an imbalance supply like the power being turned on & Off but this is less likely.
    – Ed Beal
    Feb 23, 2017 at 13:59
  • Is that a typo, or did you really press the test button instead of the reset button?
    – brhans
    Feb 23, 2017 at 15:11
  • Does the fluorescent light make an audible hum when on? Feb 23, 2017 at 15:24
  • Yes, it was a typo! I meant reset! The bulb does make a noticeable hum when on. I also unhooked the cable from outlet (LOAD) to the light and the GFCI did NOT trip. I'm just wondering if it's common for the ballast/fixture/light to suddenly become defective and would it be safe to pigtail both cables into the LINE side of the outlet.
    – Big Dog
    Feb 23, 2017 at 15:58

1 Answer 1


People often get very confused by GFCI trips

We install ground fault detectors (that's RCD to you Brits), but then we're caught off guard when we actually catch one!

If a GFCI repeatedly trips, then an appliance downstream or the wiring probably has a ground fault.

Then it's a matter of divide and conquer. Break things out of the circuit until you find the culprit.

My hunch is it's an old or cheap fluorescent ballast. 1000bulbs.com stocks a huge variety.

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