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I am trying to change a couple of switches which are in the same junction box. They control the light on my deck and the flood lights on the corners of the house. I took out the first switch - it had a black wire (1) stuck into a hole in the back of the switch, and another black wire (2) on a screw on the top right of the switch. (there is another screw on the top left, but no wire connected.) Since the wire in the box is too large to fit into the holes on the back of my new switch, I decided to take wire 1 and attach it to the bottom screw on the new switch, and wire 2 on the top screw of the new switch, since it was on top before. Then I loosened the second old switch, only to find that wire 2 from the other switch was in a hole in the back of this other switch. There was another black wire (3) in the other hole in the back, and then yet another black wire(4) on the screw on the top right of the old switch. Gah! A call to my brother-in-law later, I decided to attach wires 2 and 3 together on the top right screw (he said I could do that??) and then attach wire 4 to the bottom screw. Breaker back on - no light :(
Does anyone have any idea what i need to do?

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it'd help if you'd draw a picture. the "hole in the back" is almost always an alternate to the screw beside it, allowing easier installation. you should look into how exactly a switch works. finally, i'd recommend buying a non-contact voltage tester; it'll tell you which wire(s) are from the source (prob wire 2) and which are going to the lights. –  jberger Nov 3 '12 at 19:07
    
A picture is worth 1000 words, but at the very least, describe which wires that go to holes in back go to top and which to bottom. Also, are there any other switches in the house that control these same lights? BTW, most switches do not have screw terminals to accept more than one wire connection per screw. To connect more wires without more terminals, you should connect all the wires together with a wire nut, including a short piece going to the screw terminal. –  bcworkz Nov 3 '12 at 21:31
    
Generally, to replace simple single pole switches, connect all wires that went to the top of the old switch to the top of the new switch, regardless if they are to screws or holes. The two connection methods on the same end tie together inside. Do the same for the bottom wires. Hopefully you remember which wires went where. –  bcworkz Nov 3 '12 at 21:38
    
All of the wires were black. I have a non-contact voltage sensor, but I guess that's different from a voltage tester. I've replaced practically every light in our house over the years, and never had trouble. The wires are always color coded, so that helps. After researching how to replace a switch, I assumed that the wires would be colored, but you know what happens when you assume :) Thanks for all the advice. –  karen Nov 3 '12 at 22:20
    
Are there any white wires in the box at all (likely all attached together)? –  Tester101 Nov 3 '12 at 22:54
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1 Answer

First off, your brother-in-law is wrong. You cannot attach two wires to a single screw terminal (unless it is rated for that, which most switches are not).

Here's what I'm guessing you're dealing with. Remember it's only a guess since I'm not there and you haven't supplied a picture, or drawing.

Lets call the first switch you mentioned S1, and the other S2, then we'll use the numbers you mentioned above as the wire numbers.

  • Wire 4 that was attached to the screw on S2 might be power from the breaker.
  • Wire 2 that is connected from S2 to S1, might supply power to S1.
  • Wire 1 and 3 would then be switched hot wires feeding the lights.

You should also have 3 white wires connected together, and possibly 3 bare or green wires connected together. The white wires are neutrals, one from the breaker, and one going out to each light. The bare or green wires are equipment ground, and should be connected in a similar way as the neutrals.

If I'm correct, you should connect wire 4 and two lengths of scrap wire (~6" or so) using a twist on wire connector or other approved method. The scrap pieces of wire; or pigtails, should be made from a similar thickness and type of wire as wire 4. Next, connect one pigtail to each switch. Finally, attach wire 1 to S1 and wire 3 to S2.

Always make sure the power is off, before working on any electrical circuit. And if you need help, please contact a qualified Electrician.

Also don't forget. I'm not there, and I only have your brief description to go on. So I could be wrong.

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sounds like a good plan to me. There probably is a hot feed, shared by the two switches, with all the neutrals connected in the back of the box. –  shirlock homes Nov 4 '12 at 11:42
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