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Installing Separate Switches for a Bathroom Exhaust Fan/Light Combo and a Vanity Light

February 16, 2007

We get called out a lot and receive numerous emails for this type of project. This is a pretty simple project to complete.

The first thing you need to do is check with your local building codes department to ensure you are able to do this work legally. Some areas allow homeowners to complete electrical wiring projects on their own homes and others areas have restrictions.

The next step is to turn off the power to this circuit and verify the power is off with a voltage tester.

There are a few ways you can do this. The first depends on your existing switch box’s cubic inch size and amount of wires currently in the box. There are numerous different single box sizes. If you are unsure if your box is full, look at the back of your box and you will find a cubic inch rating. You may submit this information along with the number and size of your wires that are currently in this box in the comment section of this post and I will calculate this for you.

Typically, the power is run from the switch to the vanity light and then to the exhaust fan. If the switch box is not full, I would remove the 2 conductor cable going to the vanity light and install a new 3 conductor cable with a ground. If there is attic space above or an unfinished basement or crawl space below, you can fish the wires. If not, then you need to open up some sheetrock.

Terminating these wires depends on your existing wiring. If the power originates in the switch box, splice the grounds (bare copper wires) together and leave a pigtail to attach to the switch. Next splice the neutrals (white wires) together. Now connect the red wire to the switch that will operate your vanity light and the black wire to the new switch for your exhaust fan. Use the existing hot wire to supply power to both switches.

In the vanity light box, splice the grounds together and attach to the ground wire on the light fixture. Splice all of the neutrals together and connect to the neutral wire on the light fixture. The black wires will splice together and tuck back into the box. Finally, connect the red wire to the vanity light.

If the power originates in the vanity light box, then you need to mark the white wire as a hot and use it to supply power to both switches. The easiest way to mark the white wire as a hot is with a black permanent marker or black electrical tape. This wire needs to be marked in both boxes or on both ends. The red wire will terminate to the switch for the vanity light and the black wire will terminate to the new switch for the exhaust fan.

In the vanity light box, the grounds splice together and connect to the ground wire on the light fixture. The neutral from your power supply cable and to the fan splice together and connect to the neutral on the light fixture. The black from the 3 conductor cable will splice to the black wire going to the fan and tuck back into the box. The red wire from the 3 conductor cable connects to the light. Finally, the white wire from the 3 conductor, that you marked as a hot will splice to the black power supply wire.

If you existing switch box is full, you need to remove it and install a larger box. Now just run either a 2 conductor or 3 conductor cable to the exhaust fan/light combo. If you run a 2 conductor cable, your fan and light will come on at the same time. If you run a 3 conductor cable, you can switch the fan and light separately. I recommend the 3 conductor cable. You don’t need to switch the fan and light separately, but this gives you the option to do so at a later date.

As for the switch, I recommend a spring wound timer or other type of fan rated timer switch. The timer switch will allow you to turn it on to remove odors or steam and it will automatically turn off after a set period of time.

If you need further assistance with this project, please submit your questions in the comment section of this post. 


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8 Responses to “Installing Separate Switches for a Bathroom Exhaust Fan/Light Combo and a Vanity Light”

  1. Misty on February 16th, 2007 8:23 pm

    Hi there,

    I have a question about grounding. I am installing an outdoor Access Point to create a wifi hotspot. The unit has a green ground wire coming off it and the company I purchased the unit from tells me “you have to connect the Outdoor AP to the same grounding system with the AC wall outlet.” How do I go about doing this? Can I just connect the green wire to the screw on the electrical faceplate?

    I think your blog is cool by the way, great to see an electrician in the blogging world.

  2. Misty on February 16th, 2007 8:30 pm

    I just read through some of your archives and saw that you have another website for submitting these questions. Sorry about that, wasn’t sure where I was suppose to ask the question.


  3. Administrator on February 17th, 2007 9:55 pm

    Hello Misty,

    Thank you for your electrical question.

    Grounding is very tricky and best left to a licensed electrician.

    Providing your electrical system is properly grounded, I would run the wire back to your breaker box or outside main disconnect.

    The NEC also permits you to connect this to a point in your electrical system that a grounding wire is bonded to. For example, water pipe (within 5 feet of the meter), ground rod, etc.

    This ground wire needs to be properly installed to protect your AP and everything on your network. You may also properly install your ground wire and your electrical system may not be properly grounded. A licensed electrician can check this out for your and make things safe.

    My accountant’s wireless AP got hit by lightning which “fried” all of her computers and everything else on the network. The wireless internet installer did not ground the antenna.

  4. Scott on March 3rd, 2007 4:10 pm


    My existing vanity light and exaust fan and a recepticle on the other side of the wall from the bathroom is now not working. How can I repair this?

  5. Administrator on March 3rd, 2007 9:01 pm

    Hey Scott,

    Thank you for your electrical question.

    It sounds like you have a tripped GFCI. This is either a receptacle with a trip and reset button in this or another bathroom in your home or a circuit breaker with a trip button on it in your breaker box. In either case, you just need to reset it. On the receptacle, just push the reset button. For the circuit breaker, just turn the breaker off and then back on.

    If this doesn’t do it, then you have a wiring problem and I need more information.

  6. Phil on February 28th, 2011 8:58 pm


    I have a combo bathroom fan and vanity light in my bathroom. The fan and the light are each controlled by a seperate switch. When I open the unit from the bathroom side, I see that the light and the fan plug into an internal outlet that is part of the fan unit. When I needed to replace the fan motor, I was able to unplug the motor from inside the unit and it was a simple fix. From the attic, I see one cable running into the unit. I would like to install an additional light in the bathroom. I would like to have the new light controlled by the same switch as the light in the combo unit. I did not expect to see one wire going into the fan unit. How would I wire this setup? Thanks for your help.

  7. Dan on August 4th, 2011 10:27 pm

    how would I hook up a fan to a new switch to a existing switch for power? with a 2 cable wire.

  8. Wesley Pulst on January 8th, 2012 2:34 pm

    I have installed hundreds of light switches and plug in’s but this one has me stumped. It is a switch for my bathroom for the ceiling light, exhaust fan, and heater fan. After I installede the switch, the switches for the fan and heater work but NOT the light. I can’t see anything different to do. Please help!
    Thank You
    Wes Pulst