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I've got a couple of sets of 3 way switches in my house that aren't functioning properly. Basically, one switch has to be in the "up" position for the other switch to control the light. In the set pictured, the metal box is the existing/untouched switch 1, the blue is a new box and relocated switch 2. If switch 1 is down, the light is dead and switch 2 has no effect. If switch 1 is up, switch 2 can turn the light on an off. Aside from the taped neutrals with no wire nut and overall sloppy install of switch 1, what is wrong with the wire placement?

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    One of our resident sparkies will come along shortly and give you a spot-on answer, but you can try swapping the wires on them until it works. I've done so many times without the ability to instantly diagnose the situation like they can. Worst case scenario your breaker won't turn back on and you have to undo the last change.
    – isherwood
    Commented Jan 21, 2020 at 14:55
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    @isherwood - Suggesting trial and error electrical wiring is the most terrible advice you could give.
    – Michael Karas ♦
    Commented Jan 21, 2020 at 16:09
  • Not with three-ways. There's not much that can go wrong if the breaker is off. Trust me, I could offer much worse advice. :D
    – isherwood
    Commented Jan 21, 2020 at 16:10
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    I'll agree with 3-ways, worst thing is the light will turn on wacky... but you lost me at "Worst case your breaker won't turn back on". If you're risking a bolted fault, it's time to stop experimenting. The worst case is actually that the protection will fail to work because it exposes a latent fault in the wiring.
    – Harper - Reinstate Monica
    Commented Jan 21, 2020 at 20:59
  • Can you post a photo of the inside of the box for the light please?
    – ThreePhaseEel
    Commented Jan 21, 2020 at 23:42

3 Answers 3

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Rather than melt your brain with white, black, red blah blah, let's call travelers yellow. Here's how a 3-way circuit actually works.

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Golly, that's simple. Align the two switches onto the same yellow wire, light lights. Easy peasy.

But of course, they don't make cables in yellow-yellow-white. They only make them in black-white-red; and; depending on the other needs of the circuit, the two travelers might be any combination of colors. That's what colored electrical tape is for. $5 will get you a 5-pack of 5 colors.

Identify the travelers. Travelers are

  • always in the same cable (so might the third wire, but it won't be that way on both ends).
  • On the brass switch screws if the circuit is wired correctly

Assuming your lower switch is untouched, black and red are your travelers in this circuit. I would remark them with yellow on both ends.

Then, it's dog simple: yellow wires to brass screws, remaining wire to remaining screw and Bob's your uncle.

3-way switches don't take neutral wires, so the white wire in the blue box is definitely not a neutral. It must be re-marked a color. (any color but gray or green, but it's preferable to mark it for its function: black always-hot, red switched-hot).

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If the metal box/switch in untouched, then the 2 travelers, black & red, connected to the two brass screws on that switch should go to the other switch in the blue box and be connected to the same two brass screws. They're not. You've got white and red to those two screws. Try swapping the white and black wires. If all works right tape the travelers at each location with some yellow tape or someone on this site will yell at you.

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    The white wire should be marked with black tape as well.
    – JPhi1618
    Commented Jan 21, 2020 at 15:18
  • Thanks, Jack. Makes sense.. I was nervous to try swapping things around without really knowing what I was doing. And I obviously didn't pay attention to the orientation of the wires when I removed the old switch. Will swap them around this evening and let the forum know how it goes.
    – clwhoops44
    Commented Jan 21, 2020 at 15:19
  • @JPhi1618 Yep. another one of those "it's obvious" when it really isn't.... thanks.
    – JACK
    Commented Jan 21, 2020 at 15:22
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The blacked terminal screw denotes the common on the switch, which goes to the live feed in on one, and the live out to the light on the other. The two wires that go between the two switched terminals are called 'travelers' and since you've got a black and a red on one, those same two wires should be at the two switched terminal on the other switch.

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Image from here

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  • The orientation of this circuit is different from the one pictured. I wired in a new, separate 3 way switch setup last night that goes from switch to switch, then to the light (as pictured) and it works as intended. This one, I'm not certain if the light is first or in the middle, but it is definitely not last. It seems as though the white wire may actually be the common in switch 2? Will try that when I get home. Thanks
    – clwhoops44
    Commented Jan 21, 2020 at 15:15
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    Rather than bringing the neutral 'forward' to the second box and the light, the switched live may be carried back to the first box by one of the wires - if it's the white it needs to be sleeved or taped to mark it as live.
    – Phil G
    Commented Jan 21, 2020 at 15:24
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    There are probably about a half dozen ways to wire up 3-way switches. The diagram above is my favorite way: Power in on one switch 14/3 to the other switch and from there to the fixture(s), no "code taping" needed. Conceptually straight forward. But sometimes you end up with power-in & the switched wired to the fixture(s) in the same box. Also, an older practice was to run power to the fixture box and then a switch leg to the switch, that really complicated 3 way switches and required lots of "code taping" to properly mark the wire. Best to take it all apart and sort it out properly.
    – George Anderson
    Commented Jan 22, 2020 at 2:25

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