I moved a three way switch and (stupidly) did not take a picture of the original installation. I'm trying to put it back together and having difficulty. This was originally wired in 1980 and worked. I didn't remove or add any cables.
I have power, one light, 4 conductor cable, and 3-way switch in Box A.
I have two lights, 4 conductor cable, and 3-way switch in Box B.
I moved Box B but I've since taken apart Box A trying to figure this out so I'm re-wiring everything.
How should this go back together? I've wired a 3-way switch before and I can wire it OK if I omit the lights in Box B. I think the neutral in Box B needs to be connected to the grounding cable but I'm not sure.
- Hot (black)
- Neutral (dashed)
- Red (traveler)
- Green (bare ground)
Best Answer
The last guy used an illegal and unsafe technique to do that.
Smart switch method
Smart switch on box A switches the switched-hot. This leaves the black wire in the /3 (RBWg) spare. Smart switch remote in box B controls switch A using that wire as needed.
You need to select the smart switch pair carefully. Such a smart switch would either use the black as an always-hot and communicate via powerline or radio with the master. Or be battery or inline powered and use the black as a data cable.
Added wires method(s)
If you can switch to /4, you can have 2 messengers (red/black here), neutral (white), and a switched-hot (blue), and it will look like this.
If you can't get /4 you can just double back with a /2 cable and have the /2 carry switched-hot and its partner neutral for light A. It could transit through box A, but the hot and neutral would need to be separated from the other wires in the box. That is because in any cable, currents must be equal (cancel each other out).