Yesterday I replaced an old light fixture in my bathroom, and now the new light powers on with the breaker, but the wall switch does nothing. I'm not sure if the power is going to the switch first or the light box, but when I pulled the old light off, there were three wire bundles, all black. I made sure to leave the bundled wires together and used a voltage tester to figure out which were hot. One wire bundle was hot and one was cold, and the 3rd singular wire was also hot. So I put the hot wires together and paired them with the black wires on the new light and took the one cold bundle and paired it to the white wires on the new light. I'm confused as to which wire controls the switch and where it should go.

  • WHY didn't you just put the new light back the same way the old one was??? Can you go back and do that? Jun 23, 2015 at 0:58
  • I thought that I did! I clearly did something wrong though since the switch worked before and now it doesn't. Shouldn't both hot wires be together with the black wire from the new lamp??
    – Jwormy
    Jun 23, 2015 at 1:02
  • No, they should be exactly how they were before if it worked. You are overthinking this. Why would you think something was wired wrong if it worked before? ....... The switch leg should be wired to the light hot, not the constant hots to the light hot. Jun 23, 2015 at 1:06
  • I understand, what I'm telling you is That don't remember how it was before and I didn't take a photo. I thought I had put it back together the way it was but clearly that's not the case. I just need to know which hot wires are which and if they are supposed to be together.
    – Jwormy
    Jun 23, 2015 at 1:28
  • 1
    You need to turn off the power and check for continuity first. Identify the switch loop cable first. If this is not possible my only advice is to hire an electrician to figure it out. It'll probably only take 15 minutes and you'll just have a service call. Jun 23, 2015 at 2:50

1 Answer 1


You inadvertently bypassed the switch loop that controls that light fixture. There will most likely be a cable with a white wire that is not connected to any other white wire -- that cable is the switch loop in all but the newest installations.

  • You nailed it! I saw the white cable so I immediately assumed it was negative and I had the two mixed up. Realized the single cable was the switch. Thanks for your help!
    – Jwormy
    Jun 23, 2015 at 3:04

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