Usual story of remodeling etc. Replaced all the other 4 ways and 3 ways near it just fine, then I run into this guy. It's a 3-way, and I could have sworn I put all the wires exactly where they were on the one I replaced (which worked fine before.) So as it sits replaced, it's not working/switching, but the other end of the 3-way switch I replaced does just fine.

Now I'm at a point where beyond just color matching the normal red/white/black (since in this case I have two blacks and one red) I'm not sure what causing this. I have the red & black you see in the picture from the top wire group, and the additional black wire heading out the other way (see pictures.)

My question would be; Do I just have a bad switch and need to run and get another to make it happy again? Do I swap the two black wires? If I swap them is there possibility of damage?

We just moved in a couple days ago and my meter is in a box god knows where so I can't even test for lives, but I only do one switch at a time and test in between because I'm anal about this sort of thing. Any advice?

enter image description here

  • 3
    If the old switch worked, and you're concerned that the new one might be defective, put the old one back in and see if it works.
    – Ecnerwal
    Nov 20, 2013 at 21:49

1 Answer 1


It sounds like your wiring is like this:

three-way circuit

I believe the switch you took a picture of is the one on the left. If so, it looks like it's wired correctly: the black screw is usually common, and it seems to be coming from the red wire nut, which is the power source (am I seeing that correctly?)

If the other switch is turning on/off the light, regardless of which position this switch is in, then it is very likely this is a defective switch.

However, if it is only happening when this switch is in one particular position, then it's highly likely one of the two switches has the common wire connected to one of the traveller terminals. It could be either one.

If you can determine which wire goes where (the biggest hint is that the traveller wire is 14-3 while the others usually aren't), then you should be able to match it up to the wiring diagram here.

  • @Ecnerwal - Very valid, and I thought of that, but.. all of them were quick wired and I just cut them off and threw them in a pile with the others (wasn't thinking at the time.) I did find that if the currently not working switch is flipped to what I would expect to be on, than the other switch does NOT work. So now I'm just confused since I would still expect the red/black from one group (like gregmac shows) to be the travelers...can I swap the two blacks and test it without risking sparks and ouches?
    – Chris W.
    Nov 22, 2013 at 2:17
  • @ChrisW. if the light is on, you can flip either switch and it turns off, correct? If so, that is for sure a traveller and common are swapped. It could be on either switch, so don't assume it's this one (as I said, the wiring on this one actually looks right based on the picture you took, though it's hard to be certain).
    – gregmac
    Nov 22, 2013 at 15:41
  • As far as safety goes, that's tough. It should be obvious, but turn off the breaker when you are touching or changing any wiring. Use your non-contact voltage sensor (don't have one? go buy one now. seriously) to verify the power is off. If all this wiring is on a single breaker (99.9% of the time it will be) then there's not a huge risk of anything really bad happening, if you wire it wrong, the breaker will blow immediately. More likely, if you swap the common/travellers wrong again you'll just continue to have the same non-working setup. If you're at all unsure, call an electrician in.
    – gregmac
    Nov 22, 2013 at 15:44
  • I haven't got come back to this yet but the current configuration you have switch1--light--switch2, so if switch1 is ON, then switch2 will turn the light on and off. If switch1 is OFF then switch2 does nothing. I'll have to investigate further. Thanks!
    – Chris W.
    Nov 26, 2013 at 22:25

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