new here.

Last night, I checked out this light switch and noticed the presence of what I thought was a neutral wire. Seeing this, I ordered a smart switch to install.

Coming back now though, I'm extremely confused as to how this is wired. The previously connected wires were two black wires and one red wire (although it only controls one light and that's it). Can anyone point me to where I would find the load, neutral, and ground wires here? I suspect this was wired incorrectly by whoever built the house.

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  • Is there an additional switch for that light? Jan 6 at 21:26
  • The two blacks should be hot, one coming in, and one going someplace else. The red should be switch hot, and your lucky day you do have neutral(white) there also. Does the old switch only have two screws plus ground, or three screws plus ground?
    – crip659
    Jan 6 at 21:26
  • Do you have a picture of the old switch, showing both sides? Jan 6 at 21:29
  • Please edit to include pictures showing HOW the switch and wires are connected. Have you tested the voltage from the other colored wires to ground with the circuit power on? If so, report those as well
    – Ecnerwal
    Jan 6 at 21:29
  • @crip659 Thanks for the explanation! The old switch has three screws on it, I attached pictures of how it was wired below. Two black wires on one side, red on the other. Photos of the old switch here: imgur.com/a/WaemKTx
    – SprintKeyz
    Jan 6 at 21:40

1 Answer 1


Appears to be a bog-standard three way switch. Meaning another switch also controls the same one light.

Depending which "end" of the 3-way you are at, the black on the black screw and the white that's in same cable as it is EITHER go to the light (load), or come from the power source. The other thing happens at the other end (switch) of the 3-way. Load and power source will NOT be found in the same switch box for this version of 3-way wiring.

The Black and Red on the Brass screws are "travelers", and run with the white neutral grouped with them in their cable to the other 3-way switch location.

Green wire, that should be your ground (it's not very obvious in your pictures, but it's lurking.)

  • So I do actually have a 3 way capable smart switch, and your answer completely makes sense now. I think I can wire this switch like I would a standard 3-way smart switch, but is there an easy way to identify whether I have the line or load switch here? (I have a multimeter). The other switch is actually buried in the wall somewhere and I don't know where it is and can't access it. I actually had to flip this switch around 180 degrees to get it to turn on and off in the correct direction, which now makes sense given the apparent presence of a hidden switch.
    – SprintKeyz
    Jan 7 at 17:36
  • Multimeter, check voltage from the black screw wire to neutral. If it does not change with the switch, you are on the line end. if it does change with the switch, you are on the load end. Or if it's sitting disconnected (given the pictures) the line end should be 120V to neutral on that wire, 0V on all other wires; and the load end would be 0 on that wire, and 120V to neutral on one of the travelers.
    – Ecnerwal
    Jan 7 at 21:22

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