Why does my light switch have three wires and a ground wire?

I am switching out a light switch and I found that it has three wires and a fourth if you count the ground wire. The really odd thing is, I replaced a switch and instead of turning the closet light on and off it is turning the room light on and off. Do you have any suggestions.

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  • 1 decade ago
    Favorite Answer

    Thats the way modern houses are wired, everything is wired in a circuit, (a loop) it can be quiet tricky working out what wire goes where, you are best leaving it to someone who understands.

    Source(s): Electrical wiring experience
  • Amy R
    Lv 7
    1 decade ago

    Except for the change in light control, I would say this was a dimmer switch wiring or wiring for a ceiling fan for the main room, but it has to be that they were going to put a double switch there when they were wiring but changed their minds when they were installing the switch boxes. It could also be a remodeling issue if the closet was added later. You should try capping two of the non-ground wires together and wire the switch with the ground and the remaining wire. Number each wire with a masking tape tage before you start and rotate which wire is hooked up how - it could take three tries to get the right wires hooked up. If the extra wires were not connected to each other initially, you can try just capping each of them, but the ceiling light may not work then and the entire thing may not work then, depending on the circuit.

  • Dan H
    Lv 7
    1 decade ago

    Option 1: You switched some wires around and now you need to figure it all out. Are there two switches in the same box?

    Option 2: Are there two switches in the room for the same light fixture? If so, that is a 3-way switch and requires a special switch. It has three wires plus the ground wire. Visit the library and look at an electrical wiring book to see how it is supposed to be wired.

    Option 3: Someone else was in there before you and messed things up. It now needs to be sorted out.

  • 1 decade ago

    First you need to know what wires go to what. It sounds like you have more the one curcuit in your box. if its a three way switch you should have three brass screws. one will be your hot from the panel and the other two will be your switch legs (lines leading to the device). A single pole switch only has 2 brass screws, again one is your hot from the panel the other is your switch leg. If you take the switch out and look in the back of the box you should be able to tell if there are multiple lines coming into the box. one line may be for your closet and the other may be for the room. if theres only one wire connect the black (hot) to one of the brass screws, the green (ground) to the green screw, and wire nut the white (neutral). If you have multiple lines your going to have to identify what they are, after that you can connect the wires. to identify the lines you can connect them to the switch and see if the light turns on (its easy to do this with the curcuit hot, but be carefull not to touch the brass and make sure the ground is connected so the current has some where to go besides you) well good luck.

    Source(s): electrician
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  • ?
    Lv 7
    1 decade ago

    Simple answer:

    1 wire is the live feed.

    1 wire is the live feed to the room light.

    1 wire is the switched live to the closet light.

    You'll have to put 2 wires in one connection on the switch.

    It's that simple.

  • Anonymous
    1 decade ago

    Each electrial purchase should come with instructions.

    The colour of the wire should tell you what they are and where they go.

    I think you need a professional... you clearly don't have the logical thinking required to do DIY at this level.

  • I fink
    Lv 5
    1 decade ago

    Two way switch.

  • Anonymous
    1 decade ago

    Wtf your changing wires without knowing what your doing.Thats crazy man.

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