A bathroom fan may be exhaust only, or it may be an actual bathroom fan, light, heater, or any combination thereof. If you have only an exhaust, replacing it with a heating and lighting unit may make the time you spend in the room far more pleasurable. The job requires no special training or tools. Purchase a replacement unit that is the same size as the original.
Step 1 - Disconnect Power
In the main circuit box, shut off the breaker for the room where you are working. Simply turning off the light switch is not sufficient. If necessary, run an extension cord and hook up a lamp for lighting.
Step 2 - Remove the Old Bathroom Fan, Light, Heater Unit
Put a stepladder under the project area in a safe position. You'll need to stand on the ladder for a few minutes while doing the installation, so make sure it's in a comfortable, stable position.
Most bathroom fans will have 1 to 4 screws which hold them in place. When you remove the screws, either the unit will drop down from the ceiling, or a panel will open that allows access to other fasteners—set the screws aside so you don't lose track of them.
When the unit is loose, you should be able to access the wiring. If more than one wiring circuit is already in use, note which sets of wires connect to the different features of the exhaust unit.
Step 3 - Address Any Wiring Issues
Look at the wiring that is under the removed cover. You should see a white wire, a black wire, and a blue wire. The white wire is the neutral power wire. The black wire is the main power and the blue wire is connected to a switch on the ceiling fan.
Connect the wires. The wires in the kit should be pre-stripped to the right size and the wires under the old fan should have a wire nut on them. Before proceeding, remove the existing wire nuts. Twist the two wipe wires together and put a wire nut over the bare wires to provide insulation.
Attach the black power wire from the fan to the black wire on the light kit. Use a wire nut to insulate the twisted pair of wires.
Take the blue wire from the ceiling fan if the new light kit does not have a switch on the fixture. You should find the blue wire coming from a pre-wired switch on the ceiling fan base above the new light kit's mounting area.
If you're upgrading from a plain exhaust, you might need to run additional wiring from the light switch. You'll also have several choices about the switch system, including dimmer/speed controls and multiple on/off controls.
If you're using a customized switch system, the main thing is to keep the lighting, fan, and heating circuits. Also, if you've never worked on wiring before, it's never too late to ask a friend or hire an electrician to help with this step and later ones.
Step 4 - Install the New Bathroom Fan, Light, and Heater Unit
Begin by connecting the wiring with wire nuts. The unit should come with an easy-to-follow diagram. Don't accidentally cross circuits for the different components.
In a best-case scenario, even the screw holes will line up. If yours don't, keep some small self-tapping screws on hand for creating instant trouble-free pilot holes. You could also use a drill bit for pilot holes, but self-tapping screws cost much less and are compatible with any screwdriver with the correct screw tip.
If you're screwing into any glass or plastic surfaces, make sure not to push too hard—you could cause cracks in brittle materials.
Step 5 - Test It Out
Turn everything on at full power and let the unit operate for a few minutes to test the load on the circuit. If the breaker trips immediately when you turn the unit on, you have a direct short in the wiring. Turn the breaker off and carefully check the wiring connections for exposed or crossed wires.