My bathroom dimmer switch no longer works. I found two new replacements in the basement, but am unsure which one to use, and how to wire it.
There are two black wires in the receptacle (one actually looks like a white wire, covered with black), plus a bare third wire that comes out with the other two, but is connected to a screw in the back of the receptacle.
The original (broken) switch has two black wires, which connect to the two black wires in the receptacle.
One of my replacement switches has a green wire coming out of the rear left, and two black wires coming out of the right.
The other switch has a black wire and a green wire on the left, and a black wire and a red wire on the right.
Which of these two replacement switches should I use, and how do I connect the wires?
Use the switch with the 2 black wires and the green wire (the first one you mentioned). Connect the 2 black wires as they were on the other switch (it doesn’t matter which one goes whre), and connect the green wire to the bare wire in the box (or to the screw, if that’s easier).
The green wire and the bare wire are ground wires only and have nothing to do with the light, switch or the operation there of. They are for safety and one goes to the fuse/breaker box. One may be connected to the light fixture.
Use the switch with the two black and one green wire and connect like the old switch. Connect the green wire to the bare wire (ground.) If in doubt get an electrician.
It’s for wiring it as a 2-way switch. Like when you have a light in a stairway that can be controlled by a switch at the top of the stairs or a switch at the bottom.