by Darryl Brooks

Created on: August 03, 2009

This article will explain how to replace a three-way light switch. First, some clarification is needed between a three-way switch configuration and the specific piece of equipment known as a three-way switch. If you have two switches controlling one light, this is known as a three-way switch. If you have three or more switches controlling one light, this is known as a four-way switch. In a three-way switch, there are two three-way switches. In a four-way switch, there are two three-way switches and one or more four-way switches. Got it?

If you are replacing a switch in a three-way configuration, it is definitely a three-way switch. If you are replacing a switch in a four-way configuration, it may or may not be a three-way switch. So, how do you tell? First, cut the breaker or fuse that controls the set of lights you are working on. Remove the switch plate, and unscrew the switch from the box, so you can pull it out and look at it. Besides the ground which will be a bare piece of copper, there are either three or four wires attached to the switch. If it has four wires plus the ground, it is a four-way switch and isn't covered in this article. If it has three wires, then this is a three-way switch and we can proceed.

Loosen the screws holding the wires in place and pull the old switch free. There should be the ground, a red wire, and two black wires. The white wires should be connected with a twist connecter and pushed back behind the box. When you buy the new switch, make sure it is a three-way switch. It should have the same four screws, two of which are gold, one is black, and the other is probably green.

When replacing the switch, the ground will go on the green screw. The red wire will go on one of the gold screws. One of the blacks will go on the black screw and the other will go on the other gold screw. To tell which one is which, look back where the red wire comes out of the insulating sheath. One of the black wires will be coming out of the same sheath. That is the one that goes on the other gold screw. Put the other black wire on the black screw.

Now you should be able to trip the breaker back on and test the switch before putting everything back in place. If the light doesn't come on, or stays on, you probably have reversed the two black wires.

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