1

I just moved into this house. There's a 3 way switch that I can't figure out how to rewire it.When I turn it on at the bottom of the stairs, I can turn it off at the top of the stairs. But after doing that it won't be able to turn back on at the bottom of the stairs unless I switch it back on at the top of the stairs. I included a picture of how previous owner wired it, also a picture of all the wire combinations I tried. "Not Work" - lights won't turn on. "Worked"- light will turn on but still the same problem. So I hope someone can tell me how to rewire it. Thanks enter image description here enter image description here

8
  • Have you tested both switches? the comm should connect to one terminal in one position and the other terminal in the other position.
    – Solar Mike
    Aug 9 '19 at 15:41
  • T: top switch B: bottom switch Isn't the Black wire always suppose to be on the common terminal?
    – oliveoil10
    Aug 9 '19 at 16:13
  • Use a multimeter.
    – Solar Mike
    Aug 9 '19 at 16:14
  • 1
    How did you identify the common wire? Actually seeing a black screw, or inference based on screw position? Wire colors are semi-meaningless .. but very meaningless in 3-ways. Aug 9 '19 at 21:34
  • Do you have a multimeter? Aug 9 '19 at 22:53
2

Several wires in a sheath is called a cable. The difference gets important fast.

Traveler wires

First, it's time to stop the dizziness and confusion with the travelers. You should not have to play musical chairs with travelers. (It's not hazardous so as long as you are only exchanging the wires which belong on the 3-way, but it's a stupid waste of time). And to save us trouble later, let's mark the travelers; I recommend yellow tape, but if that color is already assigned, just use blue. Mark both travelers the same color, there is no need to distinguish them from each other.

This will always be true about travelers:

  • There is no wire-color standard. Really. That's why we mark them!
  • Both traveler wires are in the same /3 cable
  • Both traveler wires go to the 3-way switch
  • In the same /3 cable, travelers stay the same color. We don't have "crossover cables" in mains electrical.
  • However if the /3 cable is spliced somewhere, all bets are off.

So. In box 2, all 3 wires go to the switch, so that's no help at all. However in box 1's left /3 cable, red and white go to the switch. Gotcha!

Red and white get marked yellow (or blue if you prefer). In switch #1 box, and also switch #2 box, unless you have reason to believe the cable is spliced somewhere else.

Identifying the common screw terminal

You've talked a lot about screw positions and never about screw colors. On 3-ways, screw positions are meaningless. Screw colors matter. The common screw is black, the traveler screws are brass/yellow.

Now we've identified the traveler positions by logic, and identified the traveler screws by color. There is only one way this can possibly connect, and it must work. Unless:

A third 3-way (4-way), or splice in a lamp box?

Remember the part where I said "if the /3 cable is spliced in another box, all bets are off"? That could happen in a lamp box, or the site of a current or former 4-way switch. There's no substitute but to search every possible box for this. You'll recognize it when 2 wires from a /3 cable are spliced to 2 wires from another /3 cable. (Not counting grounds).

In that case, the traveler principles still apply, but you have to figure out which cable is which amongst several white /3 cables coming into that intermediate box. ...and this, this is why I advocate marking travelers with colored tape.

There's one more possibility. Here, we presume the left /3 cable connects to box 2. What if it's actually the right /3 cable??? That would make this whole thing a bodge job of considerable proportion, but it would explain a lot. The troubleshooting here might be beyond you, and it might be time to bring in a handyman.

9
  • I added a clearer picture, you mention splicing. Box 1 The cable on the right, the black and red wire is that considered spliced?
    – oliveoil10
    Aug 12 '19 at 15:48
  • @oliveoil10 splicing is any joining of 2 or more wires. You showed 3 splices in your earlier diagram and four in your latest, since you are showing the red/black tape join as separate from the wire nut. The tape join is illegal and unsafe, and should be undone and redone with a wire nut. Tape has no place in splices. It may hide something that is not a splice, like the capping off and termination of the red wire and merely taping it against the insulated black wire. Tape clumps are illegal least because they're hard to inspect. But mainly, they make poor connections. Aug 12 '19 at 18:14
  • I think previous owner taped the wires together because they were too short so that is why another black wire was attached to it then to the wire nut.
    – oliveoil10
    Aug 13 '19 at 13:27
  • Assuming switch 1 the connection of the wires is correct, If the cable on the left is connected to switch 2, is the placement of the wires correct?
    – oliveoil10
    Aug 13 '19 at 13:29
  • @oliveoil10 I cannot possibly say, because I don't know which screws are black and which are brass. Position means absolutely nothing on 3-ways. Every make and model of switch randomizes where they put common vs travelers, even two switches of the same SKU may be different. Aug 13 '19 at 16:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.