I hate 3 way switch wiring. Diagrams make sense. What’s in the gang box rarely does.

I’m also switching to Wagos because what the hell wire nuts? “Oh someone shoved 6-#14 in here? Lol good luck getting that back in when you need to add one

1. Old/Busted 2. Horror 3. New Hotness

(why yes those were 3 different types of slide dimmers before, why do you ask? Oh and one of them dimmed the under counter lighting, so that you can create the perfect mood)

Day 2. “Oh these will be easy and quick.” Hello complete mystery red wire.

I did not solve the mystery. This was a simple switch to switch replacement (no smarts) so I just wired it back how it was.

It's a three-way configuration. For that bundle of wires, the black wire is your hot to the switch. The white and red are hot coming out of the switch, and the switch on the front switches power between the white and the red wire.

I didn't post a picture of the mystery wire box :) it was joined to the other pole of a single switch (other pole of switch went to hot from panel). It maybe controls a plug but I can't figure out which one, and red would be odd for that...

If you're sure about the direction of that circuit, then I'm not sure. My first assumption (to be checked) would be that the red was the hot *in* from an Edison circuit configuration (cf. twielectric.com/safety-and-e…). Do you have any breakers with tied handles?

That said, red isn't *so* strange to use for hot in general. Related: when we moved in, our house had a mystery switch that -- I've checked -- controls nothing. No outlet, no light, no fan. I tried tracing the wire in the attic, but it goes into a space too tight to access.