I’m pretty sure I have a carter 3-way switch setup. Each box has a hot wire and I haven’t been able to wire this up successfully, either the breaker blows, the light is always on with no dimming functionality or no light at all. One box has K&T and the other is newer wiring (I live in a 1900s home).

I guess my question is are dimmers w/companions compatible with a carter setup?

  • 1
    I learn something here almost every day. Never heard of a "carter 3-way setup". Did a quick search and yowza! What a terrible idea. I found this link which explains it pretty well: nickmarkowitz.blogspot.com/2015/03/… Dec 6, 2020 at 14:09
  • I understand the setup and it’s not up to code any longer, but that’s what you inherit with old homes. Just wanting to understand if the dimmers w/ companions are compatible in this set up.
    – awvickers
    Dec 6, 2020 at 14:13
  • @GeorgeAnderson that was the first i found as well. can't believe this was a thing. here is a good video i found. youtube.com/watch?v=emTOZXlpBII
    – RadioSpace
    Dec 6, 2020 at 14:23
  • Can you post photos of the insides of the boxes involved? Dec 6, 2020 at 18:20

1 Answer 1


i never heard of a carter 3-way. so i looked it up. I am very sorry.

the short answer: no, rewire the whole thing. carter 3ways where banned in 1923. and are very dangerous.

however, to identify the wires at each box

with a multimeter 2 wires should read 120v the third is the light to be controlled. and the hot and neutral go on the "Traveler" screws. and the light(load) goes on the common screw. (this is for the horribly unsafe carter 3 way)

what's happening is you are swapping the hot and neutral. so you have to think. can a dimmer work on the neutral side of a load? no, no it can't. they only work on the hot side of the load (light).

also. don't change light bulbs without turning off the circuit at the panel.

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