Need help wiring a smart switch

fixit_fiona

I recently moved into a new home that was built in the early 80's. I attempted to install a smart switch that requires a neutral wire. When I checked the existing switch (prior to purchasing the smart switch), I found a red, white, black and ground attached to the box. The smart switch has all three of these and a ground connector, but when I connected it up, it doesn't work, NOT getting power some how. When I checked the ceiling fixture, it...

Originally asked by Scott on Stack Exchange (diy) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

Short version: that box almost certainly has no neutral at all — you are looking at a 3-way (two-location) circuit, and the white and red are travelers, not a neutral and a switched hot. The clues are already in your description: The old switch had three wires on it plus ground. A single-pole switch only ever uses two. Three terminals = 3-way. A 3-way switch box only has a neutral if a neutral cable was pulled to it. In an early-80s house that was not required by code and rarely done. The fixture has only black/white/ground with the line connections tied there — consistent with power arriving at the fixture and two switch legs (travelers) running to your switch box. In that arrangement the...

Full answer by Xing: https://diy.stackexchange.com/a/333640 (CC BY-SA 4.0).

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