I am installing a bathroom fan/light fixture combo into an existing installation/circuit. I can't figure out why the fan won't turn on once it's hooked up and wired. My only conclusion is that it is wired improperly. Here is how it is set up:

On the wall switch, there are 3 sets of black (hot) and white (common) wires, and 2 ground wires. The grounds are tied together. I am installing 2 switches that are on one piece of hardware into the switch box.

The first set of wires has one black hooked into a lightswitch and one white capped off.

The second set of wires has a black capped off and a white capped off with the white from the first set.

The third set has a black going to the second switch and a white going to the second switch.

I have not exposed or capped off anything from the previous installation and assumed that the uncovered wires that were used for the switch before are what I should use in this installation.

In the ceiling, there are 2 whites, 2 blacks and one ground. There is one white covered with the ground, and then 2 blacks and one white covered together. The ground is capped off with the ground from the fixture. The blacks are run to the fixture accordingly, and the fixture calls for only one white from the house to be capped off with both whites from the fixture.

The 'problem' is that I have a free-floating white/common that I have had to just cap off. I'm not sure which one is supposed to be used with the fixture. I've tried both and have gotten no power to the fixture.

I don't understand why the circuit isn't completing and the fixture working. I'm hoping someone can help...

If I understand what you are telling me, you have two switches on a single yoke and in a single gang switch box. Does the switch have 3 or 4 terminal screws, not including the ground screw?

4 terminal screws. A common and a hot for each switch. And yes, you are understanding correctly. I'll try to get some pictures in a moment.

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Are the two screws on the side you have the white wire connected together by a brass tab?

They were at one point, I removed the tab as per the instructions that came with the fixture.

The fixture that was in there before had a heating element, a fan and a light with a 2-switch control for all 3. one switch went up for the fan, middle for off, down for fan and heater. The other switch just controlled the light.

On the back of the switchplate for that it has some wiring directions:

"white - common, direct to appliance
black - to black on switch
red - to heater
blue - to vent
yellow + brown - to lite"

Not sure if that is helpful at all. The fixture I'm installing only has a lite and a fan.

Also on the switchplate for the old fixture, there are 6 wires. 2 blacks - one for each switch - twisted together, a gray and a yellow for the lite switch twisted together, and a free-floating red and free-floating blue wire, both for the heat/fan switch.

err, gray = brown, sorry.

That's OK, we can fix.

What you have is someone had a light and wanted a fan/light like you. To do that they needed a 3 wire cable between the switch and the fan/light. Instead of a 3 wire they used another 2 wire. That's not according to code because the neutral has to run in the same cable as the hot. It will for the light but not for the fan or visa versa. They also had an extra wire that they didn't know what to do with. Their thinking got screwy and they tied it in with the ground.

First put a wire nut on the grounds in the switch box. Next connect all the white wires in the switch box together with a wire nut. In the fan box, connect all the whites together along with the fan/light white

Put 2 pigtails on the hot black in switch box. Connect these pigtails to the screws on one side of the switch, it doesn't matter which side.
Connect the other 2 blacks to the screws on the other side of the switch.

In the fan box, connect one black to the light black and connect the other black to the light black.

OK, they needed a 4 wire cable, still would not have been to code with two 2 wire cables. Same problem with neutral being in same cable with hot.

I'll give it a shot in the morning and get back to you. Thanks!

Instead of wire nuting on two pigtails to the hot, you probably should trash the switch and get another. Connect hot black to side with tab between screws.

You are going to need all the room you have with that switch and all the wires in the box.
While you are at it , pick up some crimp sleaves. These are little copper rings you put around ground wires and crimp to keep from coming undone. Takes less space than wire nut.

Should I get a voltmeter? "Connect hot black to side with tab between screws." which one? I'm pretty sure they're all hot..

REMOVE THE WHITE WIRE FROM THE SWITCH OR YOU COULD KILL YOURSELF!! At best you will fry the switch and trip the breaker.

If you have already tried the switch with the white wire attached and nothing happened then it is only because there was no power to the switch or the white wire that is attached to the switch is the same white wire in the ceiling box with the blue wire nut on it that is connected to nothing.

You are very lucky. I hope you read this before your luck runs out!!

It's removed...

Thanks for your quick reply! I feel a lot better now.

Regarding your question about hot wires, there are switched hots and unswitched hots. Hkstroud was talking about the unswitched hot, the black wire that brings power to the switch box and can only be turned off at the circuit breaker. The black wires that go to the fan and light are the switched hots.

From your pictures I suspect that the unswitched hot is the black wire on the left as you look at the switch box. You said that the fan did not work the way it was wired in your pictures. Did the light work?

Nothing seems to be receiving power at the fixture. I haven't messed with anything today - been too busy.

One of the cables at the switch box is bring power to the switch, the other two just run to the ceiling fixture.

A meter is a handy thing to have if you are going to be doing electrical work.

In the mean time:

Connect the fan and light in the ceiling as instructed.
At the switch box, connect all the white wires as instructed.
Pick two black wires. Connect one to one side of the switch. Connect the other to the other side of the switch.

Turn switches on. If nothing works, the hot wire is the black wire not connected to the switch.

If either the fan or the light work, the hot wire is one of the wires connect to the switch.

Connect the third black wire to the output side of the switch. If both the fan and the light work the hot is connected to the input side of the switch and you are done.

If both the fan and the light do not work, the hot is connected to the output side of the switch. Reverse the first two wires you connected. Both the fan and the light should now work.