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Box 2Box] I have a light fixture above a stairwell. There are two live switches that control it, one at the bottom of the stairs, one at the top. The wiring is relatively new about 25 years old (all copper, no knob and tube).

I removed the existing light fixture, which functioned well, with the intention to install a new fixture. I forgot to make notes on how the existing one was connected to the ceiling box. There are two black, two white wires, and one bare copper ground wire. One black wire is always live, it seems to be independent of the two switches. The other black wire and the two white wires are not live, independent of the two switches. I have a multimeter to measure the current.

I am confused as to how I am supposed to connect the new light fixture. Please help!

  • Hello, and welcome to Stack Exchange. Good description, but adding a picture would probably help more. – Daniel Griscom Jan 23 '18 at 0:07
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    Did you disconnect ALL the wires? Or just the two connected to the old fixture? – Tyson Jan 23 '18 at 0:10
  • Is there a second light fixture which also lights as part of this circuit? Have any other outlets or usage points lost power? Take the cover off one of the 3-ways. Are any of its screws live? Normally, 1 or 2 should be, depending on switch position. – Harper Jan 23 '18 at 0:33
  • I fully disconnected the light fixture. The wires are hanging out, per the picture. – Martin M Jan 23 '18 at 5:03
  • There is no second light fixture, only one, which I completely disconnected. I haven't yet taken out either of the two switches. – Martin M Jan 23 '18 at 5:04
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Ok first you're going to have to take the cover plates off the two switches and take photos.

Chances are two of those wires are meant to be hooked together as the "traveler" between switches. Or, perhaps, that one hot wire is power feed to this setup, you need send hot down some line (maybe the other black) for the circuit to work. In that case one of the whites is neutral, the other is switched hot to the bulb.

You can see a bunch of wiring options for 3 way switches at https://www.easy-do-it-yourself-home-improvements.com/3-way-switch-wiring-diagram.html

Next time, take photo before!

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Usually two 3-way switch are wired 'top to top' 'bottom to bottom' and one common goes on live and other to the appliance. Neutral is given uninterrupted to the appliance.

so you have two wires going directly from a switch to the other, a permanent live on a switch and a controlled live (going to the light) on the other switch.

Get a test-light and see wich of the live is interrupted by (both) switches wire the new fixture to it and to the common neutral

  • Ok, I will take a picture and be back here in about 12 hours. I was hoping that the switches were good as is. – Martin M Jan 23 '18 at 13:03
  • Why are we thinking about switches if it worked before the switches are right. – Ed Beal Jun 22 '18 at 10:03
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So just to wrap this up. As a non-electrical engineer I couldn't figure this out. I got an electrician. He said it was not easy, as the original setup was not correct anyway. He found a workaround solution, and after 2-3 hours, finally got it to work. It was frustrating, and slightly costly, but I learned my lesson: always take the before pics, make notes before you take it apart.

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    Thanks for closing the loop on your question. As an answer, though, this isn't a very actionable solution for other readers. Can you add details (or is the solution the part about hiring an electrician)? – fixer1234 Apr 20 '18 at 0:20
  • Unfortunately I didn't have available time to dedicate to my problem. It took the electrician almost 3 hours, I can imagine that it would take me, a beginner, many weeks of trial and error. I wish I could add detail about the issue, but all I have is that the existing wiring was incorrect to begin with. I have used this electrician many times, so I took him at his word, but unfortunately I didn't ask for more detail. But pictures are key: I will take many, more than necessary next time! – Martin M Apr 24 '18 at 0:13
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    Wow 3 hours to figure out a simple 3 way switch. I would not hire that electrician again just my opinion, if it did not work correctly prior to being opened I could see it taking a little time to trace the wires but 3 hours wow! – Ed Beal Jun 22 '18 at 10:09

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