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I have a bathroom that has two lights, both had dimmer switches. Next to the bathroom is a bedroom which is on the same circuit. So, for the sake of simplicity, let's say there are three lights:

  • Vanity
  • Shower
  • Bedroom

Recently I noticed that the Vanity light was throwing out a lot of heat, and the face plate for the bathroom light switches was hot to the touch. So I replaced the Vanity light and thought that I would replace the dimmer switches (which I don't like anyway) with regular light switches. I flipped the circuit (which I do every time I work with electrical), removed the plate, and was greeted with a rather confusing setup. There are four separate wire bundles going into the box.

switch box diagram

Here's a picture of the box:

switch box pic

Being the smart sorta guy that I am, I did not keep track of which wire went where on the old dimmer switches, but they struck me as odd in that they had two wires coming out of the back that were wire nutted onto various black/brown wires in the box, and all of the white wires are tied off in a single wire nut.

I started with regular old single pole light switches and have attempted various combinations of wiring, leaving the white/neutral wires bundled in the box, unconnected to the switches. Each combination has yielded one of the following results:

  1. Vanity light works, Shower does not, Bedroom does not.
  2. Shower works, Vanity does not, Bedroom does not.
  3. Bedroom works only when one of the bathroom switches is on, Vanity and Shower do not.

So my questions are: do I need 3-way switches here? And how in the world do I wire these things?

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Sounds like you have one black hot wire coming into the box (probably that bottom one), which passed through a hot over to your bedroom switch.

So my guess would be that you should have two of the blacks wirenutted together -- that would be the hot wire coming in to the box, and the passthrough to the bedroom light. Also in that bundle should be two pigtailed wires that go to one pole of your 2 switches.

Then the other pole of the switches would be connected to the remaining black wires. The white neutrals should remain bundled together as they are.

It looks like the ground wires also have loops in them for connecting to screw terminals, you should make sure that all of the ground wires in the box are connected together with a wire nut so you have an uninterrupted ground even if there are no switches connected, then pigtail off of that bundle to connect to the ground screw on your new switches.

Here's a diagram showing my guess at how the hots should be connected:

enter image description here

Though this is only a guess -- an easy way to identify which one is the hot wire would be to tape or wirenut the exposed ends of the wire and leave them hanging out of the box, turn on the breaker, then use your non-contact voltage sensor to see which one is hot.

There's no easy way other than trial-and-error to identify which ones go to each bathroom light and which one goes over to the bedroom.

Oh, and do remember to connect the ground to the new switches since you have a plastic box (even if the previous switches were not grounded) - I think it's required by code now, but even if not, it's a good idea - especially in a bathroom where wet hands will be touching the light switch.

  • Ah ha! So the two blacks that are wirenutted...I should have two pigtails coming off there, one for each light switch, right? – AJ. Jul 29 '15 at 0:35
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    I added a diagram that should make it a little more clear. – Johnny Jul 29 '15 at 0:53
  • As an FYI, you were exactly right, even down to which wire was the "hot." Thank you very much, all's up and working again and my family isn't mad at me any more ;-) – AJ. Jul 29 '15 at 13:43
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    Great, glad it worked out for you! I just rewired all of the outlets and switches in my house and reworked some really bad "improved" wiring from the previous owner, so I got pretty good at guessing where the wires go :) – Johnny Jul 29 '15 at 15:14

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