Electrical Wiring in the Home/3-way bathroom light/fan combo


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In the process of remodeling the home, got to a little hiccup with our bathroom fan/light combo.  Here's everything I know...

When we moved in, it all worked... haha

So there is a Fan/Light combo and a seperate vanity light in the bathroom.  The Vanity light works on it's own switch.  The fan/light combo worked off of a 3-way switch at both doors to the bathroom when we moved in, both light and fan are on one switch, not individual switches....

Ok, now I apologize ahead of time for lack of terminology and knowledge, but I'm pretty confident I should be able to figure this out.  I'm good with overall electrical work, replacing light fixtures and that sort of stuff, I take the proper precautions with breakers, but when it comes to running switches and diagnosing the wiring, I'm not so good... so bare with me.

So in the attic, there are 4 lines coming in.  3 of which were all connected to one wire nut.  (1) hot ( the feed?) (2) goes to the kitchen light & switch and (3) goes to the vanity light & switch.  So all that works.

Now comes the tricky part.  The 4th line comes in, white & black and ground (I'm assuming it's the end of the 3-way swich) how do I hook into the fan/blower combo.  I tried every possible simple configuration I could with now avail....  I tried the white of both the light and fan to the white of the 4th wire and the black and blue of the light and fan to the black of the 4th wire.  Nothing... a number of things with no luck.  Now i'm pretty sure there is a breaker associated with this 4th wire, but I can't figure out how to tell for sure...

I've included a wiring diagram for what I have left for connections.  The Red is showing the Nuetral White wires.  And all the copper ground wires from all 4 lines in the attic are combined and clamped to the fan box ground screw....

OK, according to the picture, it looks like there is just one wire coming in from the switches. It also looks like the fan and light are separate from everything else. If that is the case, the white wires connect to the white wires on the fan and light, and the black wire coming in connect to the blue and black for the fan and light.

If you have done that, there may be a problem somewhere else. Use a tester, or even a plain socket and connect it to the wires coming in from the switch. See if it goes on and off with the switches.

Another possibility is that the wire going to the switches is a switch loop, and everything is hot.  However, if you are not sure, you could get a big short circuit.  Even a 220 volt short circuit if 2 breakers are involved. If you are pretty sure that there is no power coming from the switches, you can try it.

If it is a switch loop, the white wire is a hot wire and connects to blue and black light/fan unit. The black wire connects to the black power in wire, plus whatever is already connected. The white wires from the fan and light connect to the other white wires in the box.
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Electrical Wiring in the Home

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Bob Sponaugle


Just about any home wiring question. (not appliance repair) I have done all kinds of home wiring for myself, including adding a new breaker box, etc. Please, questions from North America only. Please be specific with details.

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