I'm trying to replace a light switch with a dimmer. According to a Youtube tutorial and the installation instructions, I am expecting two black wires: one for load and one for hot. There should be two groups of wires in the box; each group has 3 wires: black, white (neutral), and copper (ground).

Upon opening the switch cover, I found three groups of wires (with the same aforementioned colors in each group). All the three bare wires are connected together on the metal box. All the three white ones are screwed together. Two of the black wires are connected together and one of them is hot.

I disconnected all three wires from the switch and I could tell only one is hot, while another black one is connected with the hot on the switch. I'm confused as to why there is an extra group of wires. This home was built recently, so I am wondering whether there might be some new standards. There is only this one switch controlling the light.

In the image below, 1 is load, 2 is hot, 3 is I don't know (what I do know is 3 is not hot)

enter image description here

enter image description here

1 Answer 1


The third set of wires is going to another device. Good chance it is a receptacle, because the switch box was closest.

You will find a receptacle that has no power right now, until you connect the black back the way it was.

I would connect the black #2 and #3 with a wire nut plus a short piece of black wire to the switch screw.

Push in connectors on the back of switches/receptacles are known to give problems later on in life.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.