Things You'll Need
Needle nose pliers
Double pole light switches, sometimes called a four-way switch, are essentially two single pole switches put together. One switch controls two separate circuits. This is typically used in a series of three switches on one circuit to control a circuit from multiple locations. A double pole switch is also used to control two lights--or a light and a fan--on separate circuits. Wiring a double pole switch to work as a single pole switch is easy, as only one side is used rather than both.
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Shut off the power to the area you are working on. Be sure to test the switch with the voltage tester to make sure there is no voltage present.
Pull out the wires present in the electrical switch box where you are going to place your light switch.
Strip the coating from the black wires back just far enough to make a loop to go around the screws on the side of the switch.
Strip the coating from the white wire far enough to twist them together. At this point you should have two black wires, two white wires and two bare wires.
Connect the ground wires-- the bare wires --together by twisting them. Twist one onto the other about 6 inches from the end of one. Thread the single wire through the grounding connector. Screw it on tightly when it reaches the twisted section.
Twist the ends of the two white wires together and screw the wire nut onto the end. Make sure no bare wire is visible, if there is, cut the end of the wire.
Fold the white wires about the height of the electrical box. Push them to the back of the box. Done properly, they should rest in the back of the box easily and taking up little room.
Attach the single protruding bare (ground) wire to the green screw at the bottom of the light switch. You will need to curl the wire slightly with the needle nose pliers, making sure the wire wraps around the screw in a clockwise direction.
Loosen the screws on one side of the light switch. Be sure not to use only top or bottom screws. Use one screw in the "On" position, and one screw on the same side in the "Off" position.
Attach the black wires to the two screws using the same clockwise wrapping technique as the ground wire. It does not matter which black wire goes on the top or bottom.
Push all the wires into the box, folding them as they go. This ensures that the switch sits correctly on the box and does not have much pressure coming from the wires.
Attach the light switch to the box with screws and put the cover plate on. Restore power and check that your light switch works.
Wrap electrical tape around the screws of the switch if you are using a metal box; this will help guard against shorts and arcing.
Never assume the power is off; check it yourself. If you have no voltage meter, you may have to switch off all the power to the house to be sure.