I installed a lighting fixture in the hall, running off an older fixture. It worked fine with the existing switches. Then I wanted to replace one of the two old switches (circa 1949) with a dimmer (lamps are dimmable LEDs).
When I took out the old switch, there were three colors of wire from the box: black, white, and red. The dimmer has two black and one green. I connected the dimmer wires to the box wires in the position they had been respectively on the old switch, but was unsure about the red/green connection. I did it, and the dimmer worked. But now when I flip the second old switch – identical to the one I replaced – it trips the breaker, and did so until the breaker wouldn't even power on.
So I removed the dimmer, and everything else on the breaker works fine – except the hall lights, which won't power on (I understand, I think, that there must be a switch connected to each outlet to close the loop in order for the lights to power).
Should I cap the red wire extending from the box, and just wire the green/ground from the new dimmer to the box?
Best Answer
It sounds like you replaced a three way switch with a two way switch and wired a traveler to the ground. Flipping the second switch created a direct short to ground that can result in enough current to damage the breaker, wiring, and other devices on the circuit. Not only can you damage parts of that circuit, you are creating a fire and electrocution risk.
There are plenty of guides on how to properly wire a 3 way switch both here and other places online, and it's typically a DIY project, but if you're making mistakes like not properly identifying a traveler vs a ground and knowing which wires are hot, I'd advise you to hire a professional to properly replace devices like this.