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I've moved into a new house and I'm replacing old motion sensors with ring floodlights. I'm not an electrician, but handy, and I've done plenty of DIY research thanks to this site so I felt confident installing them myself. However, one of the two cuts out at least once a day. This one is outside of our garden shed and is hardwired into a circuit that powers the indoor lights as well. The one working without issues is hardwired to our garage circuit.

The breaker does not trip, and the indoor lights stay on. I've taken a multimeter to the wiring and it registers ~120v from hot (black) to ground (bare wire), and then shortly later it drops to 0v. There appears to only be one GFCI outlet in the whole shed and the "reset" and "test" buttons don't seem to do anything.

I've attached some photos of what I'm working with, and I've been trying to test without the floodlight hooked up at all as well. I've also attempted to hook up a spare floodlight thinking the first was broken somehow, but it's having the same problem, and if I'm somehow losing power without them attached I'm doubtful they're the problem

enter image description here

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Album with GFCI outlet on same circuit: https://imgur.com/a/B4b1JHS

Current multimeter readings on GFCI outlet. Something is wired wrong, hot to neutral shouldn't be 120v on the load terminals, right?

Line hot to ground - 120v

Line neutral to ground - 120v

Line hot to neutral - ~2v

Load hot to ground - 120v

Load neutral to ground - 0v

Load hot to neutral - 120v

Floodlight install location readings

Hot to ground - 120v

Neutral to ground - 120v

Hot to neutral - 0v

Appreciate any suggestions

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  • Yikes! Fill that hole! Either add a GE blanking plate, or another THQP breaker such as THQP120 (possibly easier to find) or replace the existing thinline breaker with a full size THQL120. Mar 26 at 19:35
  • It's on my list of to-dos, will pick one up when I'm at the store next
    – Havegooda
    Mar 26 at 19:37
  • 2
    Sounds like a broken wire somewhere that makes connection sometimes. Usually hard to find, could be at a back stab connection at last known good working device. Wire can be broken inside of wire covering.
    – crip659
    Mar 26 at 19:41
  • Posted an album of the outlet/switch on the same circuit. The wires are pretty dang snug
    – Havegooda
    Mar 26 at 20:03
  • The last/bottom picture can be the problem. Those connections have quite a bit of rust on them, and probably causing a bad electrical connection. Would replace that outlet/device. If nothing else that rust is causing excess heat there.
    – crip659
    Mar 26 at 21:20

2 Answers 2

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Some splice in the neutral wire has failed

Your voltage readings are a clear sign of an open neutral on the outdoor part of the branch circuit, likely at a failed splice in some junction box somewhere. Now it's simply a matter of tracing the fault down.

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  • Any suggestion on how to narrow it down? There's 4 sets of cable (?) coming in/out of the junction box. There's a buncha pigtails that I haven't messed with. I tugged them but they all seemed sufficiently in place
    – Havegooda
    Mar 26 at 23:56
  • Hot to ground at 0V indicates a broken hot more than a broken neutral. If hot to ground is 120V while it's not working that indicates a broken neutral.
    – user253751
    Mar 28 at 9:07
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So it turns out there were a few issues. Ended up calling an electrician and walked through it with them.

  1. There was an in-line timer from hot water heater controller that would open only during certain hours
  2. There was a light sensor on the circuit that would only open when it was dark
  3. I had slightly mis-wired my replacement receptacle. Even if I had wired correctly, I would have been plagued with the "intermittent" failure of the floodlight to stay on due to #1 and #2.

Not a great way to spend $150 on an electricians time, but I'm just glad to have it all working again

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