I opened up my bathroom light switch and fan box to replace the switches. The light is for overhead and the fan is a standard bathroom fan.

Inside the box I found 4 sets of wires (1 black, 1 white, 1 ground per set). After measuring the voltage of each black wire, I found all 4 to be hot. When I wired up the single pole switches (1 black per side of switch with all 4 neutrals pigtailed together), not only did the light and fan not work, several outlets downstream of this particular box did not work. When tested with a 3 light outlet tester, they presented with a “hot/ ground reverse” result. When I tested the voltage of the neutral line in the same outlet, I received a small voltage reading which coincides with a “hot/ground reverse” result.

I did not take a picture of how the switches were initially wired but all 4 hot lines were used and 1 line was strung across the 2 switches (not sure which terminals). The neutrals were all pigtailed together.

I’m not quite sure where to go from here.

  • What are you using to test the wires for voltage? Jan 3, 2021 at 20:55
  • I’m using a multimeter. All 4 of the black wires are testing as hot with 125 volts.
    – Kelsey
    Jan 4, 2021 at 0:59
  • Do all four black wires come in as part of their own cables? Jan 4, 2021 at 1:04
  • 1
    Yes. They each came in their own cable with a neutral (white) and ground with each. The neutrals were all pigtailed together which I left it that way but of course didn’t take a picture of how it was originally wired.
    – Kelsey
    Jan 4, 2021 at 2:36
  • Are all the switches on at the time you tested? Jan 4, 2021 at 5:46

1 Answer 1


So the neutrals were all pigtailed together and you didn't disconnect any of them, right?? So one black wire is your always hot and is strung across both switches. It is also connected to one of the black wires that feed the outlets that are not working. The remaining two black wires go to each switch to control the light and fan. Your job, should you choose to accept it, is to determine which wire is which by process of elimination, connecting wires two at a time and see what turns on or with a good meter. Naturally, you'll be turning off the breaker every time you touch in wires.

  • I have seen folks get confused when everything tested hot because the switches were on a hot coming in and going out that also feeds the 2 switches can’t go wrong there since all the whites were pigtailed.
    – Ed Beal
    Jan 4, 2021 at 22:00

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