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Nathanm 04-29-2012 08:29 PM

Electrical help!
Hello all, and thank you in advance for any help you can provide! Here is the deal I wanted to put a bathroom exhaust fan in and was told I could come off the existing switch to cut the wire, install a junction box, tie the wires all back in adding the wires for the fan. Trouble is the bathroom light stays on with the switch off. Turn the switch on light dims and the fan now runs, switch off fan shuts off light goes bright used black to black white to white where oh where did I go wrong!?

jbfan 04-29-2012 08:31 PM

Sounds like you cut into a switch leg.
How many wires are in the switch box?

dmxtothemax 04-29-2012 08:35 PM

Sounds like the light and fan are now wired in series !
You have made a mistake in your wiring !
If the wires you tapped into,
where part of a switch loop,
That would explain it all !
You will need to reroute your wiring to a point where
there is a neutral available.
Switch loops dont usually have a neutral.
There will be one available at the light.

Nathanm 04-29-2012 08:38 PM

Thank you for the reply. I just went to check, only two wires in the switch box I'm trying to run from

jbfan 04-29-2012 08:41 PM

You can not do what you want.
You need to remove the wire you installed and connect the wires you cut back together.
Remove the light fixture and connect the wires to the fan to the same wires the fixture is connected to.
The light and fan will work at the same time.
If you need other options, then you will have to run some new wiring.

Nathanm 04-29-2012 08:46 PM

jbfan, thank you for your help I have removed the wire and rewired as it originally was. Will follow your advice and post how I get along, thanks!

k_buz 04-29-2012 09:26 PM

Is there attic above this?

If you cut the wire, you still have a junction box right? Is that J-Box going to be accessible after this is all said and done?

Nathanm 04-30-2012 06:38 AM

K_buz, yes attic is above it, yes I can access the j box

hammerlane 04-30-2012 06:59 AM

1 Attachment(s)
so currently this is what you have??

Nathanm 04-30-2012 07:05 AM

Indeed that is correct, That was the set up

hammerlane 04-30-2012 07:30 AM

1 Attachment(s)
And now you want to add a switch controlled exhaust fan? Will the switch that controls this new exhaust fan be in the same box as the switch that currently controls the light? Or are you replacing the current switch with a double toggle switch?

hammerlane 04-30-2012 07:40 AM

1 Attachment(s)
Heres another switch loop set up for the fan. This setup you have to get power into the fan box and then run the switch loop back to the switch for the fan.

As a not I do not show ground wires in the diagram just for ease of drawing.

hammerlane 04-30-2012 07:44 AM

1 Attachment(s)
Heres a setup where where the power for the exhaust fan is brought into the switch box that houses the switch for the fan.

Nathanm 04-30-2012 09:38 AM

So I will have to run another switch I can't tap into the loop behind the light for power and have both fan and light run from the one switch already installed?

kevinp22 04-30-2012 09:51 AM

you can use the existing switch loop to control the light and fan but you wont be able to control them independently. either both on or both off. even in this case, of course, you will have to run a cable from the light to the fan

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