Step 1: Make Sure the Power is Off

Before starting, make sure the power is off at the electrical panel. Remove the cover from the switch. Use an electrician's wire tester to double check that the circuit is safe to touch. Use a screwdriver to remove the switch toggle.

Step 2: Keep Track of the Wires

Once the switch is removed, use a wire nut to mark and keep track of the wires.

Step 3: Measure and Cut the Drywall

Measure to install a new double work box. Make marks on the wall, and check with a level.

Using a utility knife cut the drywall hole for the new double box.

Step 4: Pull the Wires Through the Work Box

With the wires for the light switch and exhaust fan separated, pull the wires through the new double work box and screw them into place.

Step 5: Attach the Wires

Wire the new switch and the new timer attaching the hot, neutral and ground wires for each following the manufacturer's specifications.

Step 6: Place the Switch Cover and Test

Adjust the toggle switch for the light and the shaft for the timer accordingly to make them line up with the switch cover. Then screw on the switch cover and attach the timer plate and knob. Turn on the power and test your work.