Sometimes it is necessary to control a light from two different places; for example, the top and bottom of a stairway. When wired correctly, the light can be turned on or off from either switch. This can be done with two (2) three-way switches. To control a light from more than two switches, use four-way switches. There are several ways to wire three-way switches to a fixture. This is the simplest way.
Between the fixture and the first switch, run two-wire cable. Then, between the two switches, run three-wire cable.
The feed wire (from the power source) should be two-wire and will have a black wire and a white wire. Using a wire nut, attach the white wire from the feed to the white wire at the fixture.
The black wire from the feed will run straight through the fixture to the two-wire cable running between the fixture and the first switch. Using a wire nut, attach the black wire from the feed to the white wire of the two-wire cable running between the fixture and the first switch.
Using a wire nut, attach the black wire from the fixture to the black wire of the two-wire cable running between the fixture and the first switch.
Go to the first switch. The white wire coming from the fixture should be attached to the dark coloured screw on the switch. It is a good idea to mark this screw with paint or a permanent marker to indicate that it is “hot”.
Take the red and white wires from the three-wire cable running between the two switches and attach them to the light coloured screws on the first switch.
Attach the black wire coming from the fixture directly to the black wire running between the two switches with a wire nut. The black wire should not be attached to the first switch.
Go to the second switch. Attach the red and white wires to the light coloured screws and the black wire to the dark screw.
Test your switches. You should be able to turn the fixture on or off from either switch.
When stripping your wires, only strip the amount you need. Be sure you do not have bare wires touching each other. This can cause a short, which can result in a tripped breaker, blown fuse, or (worst case scenario) fire.
Always tape connections made with wire nuts to avoid bare wires contacting other bare wires.
BE SURE TO CUT THE POWER TO THE AREA BY TRIPPING THE BREAKER OR PULLING THE FUSE BEFORE WORKING.
Always replace switch covers to avoid the risk of electric shock.