Have a 2-gang light switch in bathroom. Left switch controls vanity light. Right controls bathroom fan+light. There is also a GFCI outlet in a separate gang that may be tied into this somehow? I'm not 100% sure, but it is very close to the switches.

This was working. I swapped out the GFCI and tried to swap out the right light switch for fan+light simply because they were old and yellowed. Well, I broke it. How can I wire this correctly?!

There are 3 pieces at play here:

  1. Furthest left light switch in 2-gang. This controls vanity light I believe and appears to have two black wires on the right side. The top black wire was branched off to the right light switch (uncapped wire), and the bottom black wire appears to come from the wall. There is also another uncapped wire that was connected to the right light switch coming from the wall.

top black wire was branched to right switch from the left switch, and bottom black wire comes from wall.

  1. Right light switch. I believe this controlled the fan+light. The original switch had an input labeled "common" but I have no clue what wire went in there. Also it appears the original switch had more inputs than the switch I tried to replace it with. Maybe that's how I screwed up?

Original switch on left, new switch on right.

Original switch on left, new switch on right.

  1. The GFCI is in its own gang, about 12" to the right. This seems to work ok, but the test and reset buttons don't actually seem to do anything. The weird thing about this is when I was replacing the previous GFCI outlet, I'm not sure that both black wires were even connected. I know the white ones both were. But there may have been a black wire (the bottom black) just uncapped and not connected to the previous GFCI outlet. Or maybe I'm imagining things.

GFCI with two white and two black wires.

showing GFCI in relation to switch gang.

I tried many ways of wiring this, both with the new switch and going back to the original switch, and each time I turned on the breaker, the GFCI indicator LED would light up, but neither light switch would work. And when I took the electric tool to check for current, it wouldn't even beep that current was even running through the light switch wires. So I am at a loss here...please help.

  1. Do I need a different light switch to replace the existing one?
  2. I only have 2 black wires + ground to play with, so how did I mess this up so badly, and where do I connect those two wires?
  • Let's assume it worked before and you took a picture of the wiring, post it
    – Traveler
    Dec 23, 2022 at 7:51
  • Wish I took a picture of the wiring! I didn't. Really regret not doing that. Ugh.
    – jflbball
    Dec 23, 2022 at 12:20

1 Answer 1


This will take some examinations. It looks as if the switch that you were trying to replace was a 3way that was not used for that purpose. Thus the confusion over the common screw. Discard that. You need to find what black wire provides power to the switches. That black will get 2 pigtails two attach to one of the screws on each new switch. Or if the hot wire is long enough just transfer from one switch over to the other. The other black wires will go (one each) on the empty screw on the switches. This will supply the power to the fan/light and vanity light when switched on. If you have no hot wire in the switch box when the breaker is on, you may be running the power through the GFCI. This is not good because if there should be an event that opens the GFCI it will leave the bathroom dark. The pic of the GFCI shows power in and protected power out, ( line and load). That may not be the way the original was wired. Or you may have switched the line and load wires. Check that. It is also possible that your bath GFCI actually gets its power from another GFCI in another bathroom or some other part of the house and that GFCI is open and needs reset. This is something you need to be systematic about, but it can be rectified. Good Luck

  • Formatting!!!!!
    – FreeMan
    Jan 17 at 18:24

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