Today, I wanted to replace a dimmer with a normal switch for my dining room lights. When I pulled the dimmer out of the wall, all 3 wires just fell right off of their connections. I'm surprised the house didn't burn down years ago...

Anyways, whoever installed this did a terrible job and I'm now left with 9 wires sticking out of the wall.

  • 3 white wires bound together
  • 3 ground/copper wires bound together and connected to the dimmer's green wire with a metal "staple"
  • 3 black wires in which I do not know where they go.

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I removed the wire nut off of the white wires so I was able to see which direction they are going. 2 white wires coming from the left, 1 white wire to the right, same with the black wires.

Now, I've been trying to read up on which wires go where, but I'm stumped at this point. I know I will have to wire nut all of the white wires together, and of course run the green to the switch ground.

Where do the wires go? Do I need to use a 3 way switch even though I only have a single switch to control a single light at this point?


  • Do you have a multimeter or a voltage tester?
    – longneck
    Apr 21, 2016 at 14:33
  • Yes, I do all DC work with it. So I'm unfamiliar at best with AC. I'm following instructions in your answer right now
    – ntgCleaner
    Apr 21, 2016 at 15:10
  • They fell apart because wirenuts of decades past weren't very good. The new ones are MUUUUCH better. Apr 22, 2016 at 5:06

3 Answers 3


The simplest thing to do is to turn the breaker on and figure out which black wire is supplying the current. (This is arguably one of the more dangerous approaches, but it is safe if you follow precautions like have someone guarding the wires so they are not touched while the power is on.) Use a multimeter and test the voltage between the ground wire and every other wire. Exactly one black wire should have 120 volts on it.

If not, stop and report back here.

Once you identify which black wire is hot, turn the breaker off.

Then wire nut all of the whites together. Wire the "hot" black wire you identified to one other black wire. Turn the breaker on. Note if the ceiling light came on. If not, turn the breaker off, hook up the other black wire to the hot black wire and turn the breaker on. Note if the ceiling light came on. Turn off the breaker.

Now you know: 1. which black wire is the "hot" wire, and 2. which black wire goes to the ceiling fixture, and 3. your "other" black wire, which probably provides power to another switch or outlet.

You should wirenut the "hot" wire and the "other" wire together with a short scrap of black wire to create a pigtail. Connect the pigtail to the switch. Connect the black fixture wire to the other side of the switch. And your whites should already be wire nutted together from before. So just hook up the ground wire to the switch, and you're done!

  • The approach and methodology got this answered perfectly. I was able to find the 120v wire, tap it to find out which controlled the light and presto! The switch works. Thank you!
    – ntgCleaner
    Apr 21, 2016 at 15:19

I am guessing that if you apply a meter you will find that the single black and white on the right address power coming into this switch box, and the wires on the left run to the lights.

If so the switch installs between the left black and the right blacks, to interrupt the hot line, the whites are all tied together to provide the neutral connection (as you found them) and the greens are tied together and have a wire that goes to the switch's ground lug.

It should be safe to try that and see if my guess is correct. The worst that should happen is that one of the lights says on no matter what you do to the switch; if that happens, a different combination of the black wires is needed. The meter should tell you that, though.

(@longneck's answer is a more principles approach to this.)


Wire nut all black wires.use meter. It's safer than letting them stay open and hot. To be honest I'd check the rest of ur sockets. The arc flash burns in box is a dangerous sign

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