I just moved into my house and replacing switches and receptacles when I come across a 3 way circuit not working correctly. I pulled the 2 switches to find someone had replaced one with a single pole switch. Unfortunately they did a sloppy job and didnt pigtail their hot wires properly, so wondering if someone can tell me how to properly rewire this to my 3 way switch. Thanks in advance.enter image description hereenter image description here

  • Hello, and welcome to Home Improvement. Would you add a picture of the other switch box innards? And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Jul 26 '19 at 1:57
  • Thank you for the tour link. I have added a photo of the second switch box. – Jmak Jul 26 '19 at 2:10
  • I see that in the first photo, one of the black wires is backstabbed. Don't do that; such connections are unreliable and can cause problems. And in this case there wasn't even any need for it, as this screw clamp is designed to handle two wires. – Ray Butterworth Jul 26 '19 at 13:44

OK. A 3-way switch complex acts exactly like a plain switch. Meaning if you take the two 3-ways and the /3 cable between them, and pretend they're not there, you see what else is going on.

In this case, if you ignore the 3-ways and /3, all that's left is a /2 cable to the top box. That makes this a switch loop.

Normally, in a switch loop, the white wire carries always-hot * and the black wire carries switched-hot. Code has two things to say about this:

  • if a white wire is used as hot, and always-hot is in the cable, then the white must be always-hot*. Correct that if it's wrong.
  • A white wire used for "hot" absolutely must be marked with black tape. This has been overlooked in these boxes, so you should correct that.

It appears the last guy wired the 3-way loop with the white wire being always-hot. That is fine, but again you need to mark the white wires at each of their ends with black tape.

The remaining wires in the /3 (red and black) are travelers. I recommend you mark both travelers with yellow tape (readily available as part of 5-packs of colored tape). Travelers don't need to be distinguished from each other.

Then it's easy: On the 3-way switches, the travelers go on the brass screws, and the remaining wire (whatever it is) goes on the remaining black screw.

*The white wire is used for always-hot so a voltage tester will always show it as hot; that means it won't be confused for a neutral. The switched-hot wire will test as "at neutral" when the switch is off, because it's connected to neutral via the light bulb.

  • Thank you very much for this explanation, it finally allowed my brain to click into what was going on. I have wired in the new 3-way switches and have tape labelled the wires as you suggested. Both switches are working as intended and I can put that wall to rest now. Thank you again for your solution. – Jmak Jul 27 '19 at 23:27

I'm not able to tell what wires go where in your top picture but here's a diagram of what it should be when you're done. You'll have to identify the feed, common, load and two travelers.

enter image description here

  • That's not right. This arrangement would require a /2 and /3 cable in both boxes. Yet the second box has only one /3. – Harper - Reinstate Monica Jul 26 '19 at 5:00
  • You're correct. Just trying to illustrate the wiring of the switches.... not necessarily the position of the feed and load... – JACK Jul 26 '19 at 11:28

From your first picture, it looks like you have

  • Two black wires attached to the same terminal on the switch
  • Two white wires (incorrectly) nutted together
  • A red wire
  • Various ground nutted together (looks like metal boxes so it's OK if they're bonded to the box only)

This means you have a two-line cable and a three-line cable coming into the box. You'll need to identify the fixture and verify that the two-line cable is being used as a hot and switched hot. The white wire is likely your hot (hooked to other black wires in the fixture junction box) and the black will be your switched hot (hooked to the fixture hot). Assuming this is the case, here's how to fix it

  1. The incoming hot (white) should be hooked to the black of your three-line cable. Take a black marker or black tape and mark this wire so it's clear what it is.
  2. Hook the white and red of the three-line to the brass screws of a new three-way switch (it doesn't matter which wire goes on which brass)
  3. Hook the black screw of your new three-way to the switched black of the two-line cable

That sends the power to your correctly wired switch and establishes the travellers so the switch works again.

  • Thank you for the info. I will pull the fixture to verify that it is that way and let you know how I make out. – Jmak Jul 26 '19 at 9:49

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