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My 4-way switches work correctly. I would like help figuring out where the power is coming in from and where the light fixture is (at the end, after a certain switch, etc.) I'm also trying to understand what is happening in this electrical box where "switch B" is housed--there are 4 cables entering the box. The green line represents the white wire. enter image description here

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  • Cable 3 goes to switch A.
  • Cable 4 goes to switch C.
  • Cable 1 goes to the lamp.
  • Hot is being supplied to the entire works by the one of the black wires at switch C.
  • Neutral is supplied by cable #2.

Supplying hot and neutral in separate locations like that is bizarre and not code legal.

  • Thank you for your quick response. Those were my guesses, as well. There is actually another switch in this box whose sole purpose is to provide a ground, because switch B has no ground screw, I suppose. No other wires are attached to it. – Courtney B Mar 28 '16 at 13:20
  • Where do you think I would find the other end of cable 2? – Courtney B Mar 28 '16 at 14:14
  • Ideally the service panel, but possibly somewhere associated with that rogue black wire at switch C, or potentially anywhere he can find a neutral or ground if he's that sloppy. It sounds like this setup was improvised from an earlier wire configuration, i.e. the switch C site used to be a regular switch loop for something else. – Harper - Reinstate Monica Mar 28 '16 at 17:32
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Your setup is quite improper & illegal. So, don't touch or change anything unless you're rewiring all of it correctly. The 4-way switch (B) just connects the 2 3-way switches (A & C), it's just a bridge.

FYI, the wires with 3 wires total (black, white & ground) are supposed to be solely for the power supply (C) & light operation (A), just regular Romex cables for in & out. The wires with 4-wires total (black, red, white & ground) are usually just the 3-way switch connectors. They aren't supposed to be the power supply nor light operator & should just transfer the power from 3-way switch to 3-way switch through the 4-way switch.

Your problems are that Regular 3-wire Romex (cable 4) was used to connect (C) to (B), instead of a 4-wire cable (cable 2). And, a proper 4-wire cable (cable 3) was misused to connect (A) to (C) while also operating the light. Due to these you can't even label things uniformly.

  • Thank you for the explanation and quick response. I wanted to add another light fixture to this circuit. Could I still do that, by running cable between the lights? – Courtney B Mar 28 '16 at 13:23
  • Yes, your idea is exactly right. Add another light only by wiring it from the existing light, do not wire anything into the switching wire runs. – Iggy Mar 28 '16 at 13:36

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