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Replacing a Bath Fan Switch – Electronic Timing Device

This articles outline the steps involved in replacing a bath fan switch with an electronic timing device.  A standard single pole switch will be replaced with an electronic timing switch for the control of an exhaust fan in a bathroom.  This eliminates the problem of bath fan switches left running.

Original 4-Gang Outlet With Three Switches and GFCI Receptacle

At the time I wrote this article, we had three bathrooms in our home, and two in our business.  They all had a standard bath fan operated by a wall switch.  Their purpose is fairly straightforward.

HOWEVER …. Nothing drove my wife, Sandy, more crazy than finding one (or more) of these bathroom fans running non-stop.  It’s a pet peeve of Sandy’s if Lyle (my son) or I should leave the bath fan running after showering, or using the other facilities.  Or worse, to find that one of the office bathroom fans had been left running all weekend.

Fortunately, there is a solution – replace a standard bath fan switch with a timer switch.  This will allow you to move the moisture out of the air with your fan, but limit the fan’s operation to pre-selected intervals of 10, 20, 30 and 60 minutes (this will vary, depending upon the timer switch model and type). SO … no more wasted energy by having the fan run constantly, and no more frustration for Sandy – PERFECT!

In the example we use in this article and supplemental video, we have an existing 4-gang outlet with three switches and a ground fault receptacle in the decora or decorator device style. We will be replacing the switch that operates the bathroom fan with a Leviton electronic timing switch.

If you haven’t already watched the video of this project, you can do so via the following link:


Materials and Tools Required for the Project


  • Screwdrivers (3/8” and ¼” standard blade, and/or Phillips and Robertson as required)
  • Diagonal pliers (side-cutters)
  • Linesman pliers
  • Long Nose Pliers
  • Knife
  • Voltage testing device (multi meter, power pencil, etc.
  • Wire Strippers


  • Leviton Electronic Timing switch (or equivalent)
  • Wire Connectors

Step One – Ensure the Power is OFF Ensure that the power to the circuit is off, and arrange for an alternate light source (either battery operated, or an electric light plugged into a different circuit in another location).

Step Two – Remove Cover Plate Remove all of the screws in the 4-gang decora cover plate.

Step Three – Test the Circuit Double check with a voltmeter, power pencil, etc., to ensure that the power to the circuit is off.

Ensure Power is off to the Circuit by Testing

Step Four – Remove Existing Switch Remove the existing switch for the bath fan. Note that in this example we have a lot of wires and splices in behind the switch and thus we won’t have enough room for the new device, as it is much larger and deeper than the regular single pole switch.

Remove the Existing Bath Fan Switch

Step Five – Remove Additional Switches For the reason noted above, and the fact that the new device requires a neutral connection, we will have to remove all of the switches in this outlet box.

4-Gang Box with All Switches Removed

Step Six – Identify Required Connections With the switches now out of the way, we can determine what connections and splices that we will need access to. The new device has four (4) wires coming out of the body of the device:

        • A green ground wire
        • A white neutral wire
        • A black wire for power in
        • And a blue switched wire

Step Seven – Making the Connections

After looking over the wiring diagram that came with the timing switch (yes, reading the instructions is a must), determine what connections are required.

In the outlet box we will need to gain access to one of the ground screws in the back of the box to connect the timer’s ground wire to it.

Accessing the Ground Screw in the Box

Green Ground Wire Connected to the Ground Screw in the Box

The white wire from the timer will need to be added to the neutral splice.

White Wire Connections

The black wire needs to be added in to the splice of black wires that have pigtail wires that connect to one side of each of the existing switches, and to the line in terminal of the GFCI receptacle.

Remove the wire connector and remove the pigtail that goes to the existing bath fan switch.  In its place you need to spice in the black wire to the timer.

Black Wire From the New Timer Device Connected

Step Eight – Splicing Power to the New Timer

The black wire that was connected to the other side of the existing bath fan switch needs to be spliced to the blue wire from the timer switch.

Blue to Black Switch Leg Splice

Step Nine – Replacing the Wires Back Into the Box

Now we need to push back all of the splices into the box, making sure that you have room for the new device.

There is more space behind the single pole switches, so work the bulk of the splices in behind them, and be careful that when the devices are reinstalled, there will be no pinch points or pressure on the wires.

Tuck Splices Back With No Pinch Points or Pressure on Wires

Note that with this particular timing device, there are tabs that must be removed in order to fit within the space available in the multi-gang box.  The tabs are scored for easy removal.

Remove Tabs on Timing Device

Step Ten – Reinstall the Devices and Plate

Reinstall all of the devices.  Test fit the cover plate and adjust device positions if necessary.

Reinstall Devices and Ensure Cover Plate Fits

Step Eleven – Replace Plate and Restore Power

Reinstall the cover plate and plate screws.  Restore power and test the device.

Cover Plate On, Power Restored and Device Tested

And there you have it – an easy solution to a common household dilemma.

Wiring Diagrams:




CLICK HERE to watch a video of this project.

This entry was posted in Wiring Projects and tagged , , , , , , . Bookmark the permalink.
  • charnjit singh

    Thanks, for the easy mothod for understand wiring system.

  • sophia

    Dear sir:
    are you interested in saving some money on importing any of the following?
    -mechanical timer
    -digital timer
    this is sophia from Cixi Zicheng Electronics Co.,Ltd,a timer specialist for several years,
    all of our products are very affordable as a result of being produced in special economic development regions of China ,
    and we are more than happy to help you with the import process too!
    if you are interested in it,please feel free to connect with us
    Best Regards
    sophia Tang

    • admin

      The most important part of importing electrical devices from different countries is ensure that the devices have the appropriate approvals for your area such as U/L , CSA, or other acceptable approval agencies that are accredited to provide such an approval acceptable to the local electrical authority.

  • Wonderful to become going to your website once again, it may be months for me. Very well this post that i’re been waited for so long. I require this article to comprehensive my assignment inside the college, also it has very same subject along with your post. Thanks, wonderful share.

  • Phil Bolduc

    My old toggle switch has two black wires connected to it. How do you know which black wire goes to the fan and which black wire is the power in?

  • Mnoiqueflowers75

    i would like to know how do i wire 4 switches to to 2way switches

  • Moniqueflowers75

    that is control by 4 lights


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