Even though there are many wires to connect when wiring a bathroom vent, light and heater combination, keeping track of each wire is easier than it sounds. This is due to the color-coded wires in each of the electrical cables needed for the project. Start by installing the vent/light/heater fixture and an electrical box in the wall for a switch. When wiring the fixture, use a combination of wire connectors and electrical tape to ensure solid connections. As with any electrical project, first make certain the breaker controlling the flow of electricity to the fixture is in the "off" position.
Cut a piece of three-wire electrical cable -- containing black, red, white and ground wires -- long enough to reach from the wall switch box to the light/vent/heater fixture, using cable cutters. Cut a piece of two-wire electrical cable -- containing black, white and ground wires -- that reaches from the wall switch to the fixture. Strip the ends of all the wires in the two electrical cables, using the wire strippers, to expose 1 1/2 inches of bare wire.
Run a piece of two-wire electrical cable from the breaker box to the wall switch box. Strip the ends of all the wires in the cable to expose 1 1/2 inches of bare wire.
Insert the ends of all three cables through the holes in the switch box. Tighten the wire clamps on the box with a slotted screwdriver.
Look at the back of the switch and notice three holes on one side and one hole on the other side. Push the black wire from the two-wire cable coming from the breaker box into the hole on the side by itself. This will power the fixture's heater.
Push the red wire from the three-wire cable into the hole directly across from the black wire you just connected. Install the black wire from the three-wire cable directly under the red wire. Insert the black wire from the two-wire cable going to the fixture into the remaining hole on the switch.
Twist the stripped ends of the white wires from all three cables together, using a pair of pliers. Screw a twist-on wire connector onto the joined ends. Wrap the connection with electrical tape. Repeat the process with the ground wires from all three cables.
Push the wires into switch box, gently folding them as needed. Push the switch into the box. Secure it to the face of the box with the provided screws and a Philips screwdriver.
Connect the red wire from the fixture to the red wire from the three-wire cable, joining the ends with a wire connector and wrapping the connection with electrical tape. Join the black wire from the vent in the fixture and the black wire from the three-wire cable in the same way.
Join the black wire from the two-wire cable to the blue wire for the light with a wire connector and electrical tape as you did with the others. In the same way, connect the white wire from the two-wire cable to the white wire from the light. Connect the remaining white wires together, then secure all ground wires together, using a wire connector and electrical tape.