- Turn the breaker in the electrical panel controlling the flow of electricity to the light switch off. Measure the distance between the two switches, add about 24 inches and then add 30 percent. Cut the 12-3 cable with ground at that measurement with lineman's pliers. A hacksaw works well as a substitute if lineman's pliers are not available.
- Run the cable from the first switch box to the second. Strip 10 inches of the outer covering off with a utility knife. Feed the wires through the switch box so you have at least six inches coming out from the box.
- Strip the insulation from each of the wires to reveal one inch of bare wire. Bend the bare wire ends over to form a "U" shape with needle nose pliers. There are three wires coming to this box from the power source. They are black, white and green or bare. Feed these wires through the switch box as well.
- Hook the end of the black wire from the power source around the top terminal screw on the two-terminal side of the three-way switch with a secure it with a screwdriver. Secure the black wire from the 12-3 cable to the remaining terminal on the two-terminal side of the switch. Hook the red wire from the 12-3 cable to the terminal on the opposite side of the switch from the black wires.
- Stick the bare ends of the ground wires into a wire nut. Twist the nut in a clockwise direction until it is tight. Wrap the open end of the wire nut with electrical tape. Repeat this with the white wires.
- Connect the second three-way switch in the same manner as the first. However, instead of having three wires from the power source, they exit this switch box and travel to the fixture. The black wire going to fixture connects to the top terminal on the two-terminal side of the three-way switch.
- Push the excess wire into the switch box. Secure the switches to the switch boxes with the screwdriver. Install the switch cover plates on both switches. Turn the breaker on.
Things You Will Need
- 12-3 cable with ground
- Lineman's pliers
- Hacksaw (optional)
- Utility knife
- Wire strippers
- Needle nose pliers
- Wire nuts
- Electrical tape
- Push the excess wire into the switch box with the rubber handle of a screwdriver.