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I am trying to replace what appears to be a 3 way switch with a Sonoff switch. I say appears because no matter what I do with the switches I can not figure out what they control. I checked all outlets (top and bottom) and there are no lights for the switches to control in the room.

The Sonoff requires live and neutral. Plus whatever is being switched. Since I don't care about what is being switched and just want to use the sonoff to control via wifi a plug, all I need is to get live and neutral to the sonoff in the switch 2 location and I am good to go.

Switch 1 has a 2 wire (white/black/ground) and a 3 wire (white/black/red/ground).

Switch 2 only has a 3 wire (white/black/red/ground).

Switch 1, 3-wire white connects to Switch 2 white. Switch 1, 3-wire red connects to Switch 2 red. So I expected the above to be the travelers for the 3 way switch. Since they also connect to the "top" inputs of the switches.

Switch 1, 2-wire white is connected to the 3-wire black. The 3-wire black is connected to Switch 2 black which is connected to the common on Switch 2.

Switch 1, 2-wire black is connected to common on Switch 1.

Here is a table which might be easier to understand.

From To Same As And
sw1-2w-white sw1-3w-black sw2-3w-black sw2-common
sw1-2w-black sw1-common
sw1-3w-white sw1-topleft sw2-3w-white sw2-topleft
sw1-3w-red sw1-topright sw2-3w-red sw2-topright

What do I need to do to get live and neutral to the switch 2 so I can power the sonoff wifi switch?

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    Can you post photos of the insides of the boxes involved please?
    – ThreePhaseEel
    Sep 30, 2022 at 2:16
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    For each individual box, we need to know about each cable entering the box, and how each of its wires connects to switches and to each other. Grounds need not be reported. On switches, look closely for brass vs black screws, and words like "travelers" or "common". A backstab very near a side screw is internally connected to that side screw, and is like putting 2 wires on that screw. Diagrams would not be useless. If doing it in a drawing program, lay a light green background so white stands out.
    – Harper - Reinstate Monica
    Sep 30, 2022 at 3:17
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    "A picture is worth 1000 tables" is how I believe that old saying goes... :)
    – FreeMan
    Sep 30, 2022 at 12:30

1 Answer 1

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I ended up figuring it out. The 3 way switch was controlling an outlet that was hidden behind a cabinet. That outlet contained the line to the panel and a wire to Switch 1. Since that outlet is not accessible I removed it and connected white to white, black to black and put a blank panel on it. Then in the switch 1 location I put white to white, black to black and capped red. I then put a blank panel on that too. Finally at the switch 2 location I installed the sonoff with white and black and capped the red (now unused traveler).

Turned power on and everything worked.

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  • Sounds about right, and bonus points for knowing to use blank cover plates and not trying to bury them behind drywall!
    – FreeMan
    Sep 30, 2022 at 14:05

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