How to Replace a Light Switch
How to wire a light switch
Loosen the screws on the side of the device with a standard screwdriver (turning counterclockwise). You may find getting the wires out of the back of the device tricky. To remove these wires, insert the blade of a small screwdriver into the slot under the hole into which the wire is inserted and push in as you pull the wire loose. Pushing the blade of the screwdriver into the slot releases the grip on the inserted wire. Here are some descriptions of each wire and where they go:
The white (neutral) wire connects to the silver screw, or you place it in the back wire hole on the same side of the device as the silver screw.
The black (hot) wire goes to the brass screw or into the hole in the back of the device on the same side as the brass screw. This wire is sometimes red.
The green or bare copper (ground) wire, if the device has one, attaches to the green screw terminal on the switch or to the electrical box.
Although plug-in connections may be more convenient, they are less reliable than those with screw terminals, so don't use them!
Replacing single-pole light switches
If the switch has On and Off embossed on its body and it's the only switch that controls lights or receptacles, it's a single-pole switch. To replace this kind of switch, follow these steps:
Turn off the power to the switch at the main circuit breaker or fuse panel.
Unscrew and remove the switch plate; then use a voltage tester to make sure that the circuit is dead.
Unscrew the switch from the electrical box and pull it out with the wires still attached.
Two or three wires will be attached to the switch: an incoming hot wire, which is black; a return wire, which carries the load to the fixture and may be black, red, or any other color except green; and sometimes a grounding wire, which is green or bare copper. There may be other wires in the box, but you are only dealing with the ones connected directly to the switch.
You may find a white wire that has black tape on it connected to the switch. This tape indicates that the white wire is being used as a black or colored wire in the switch leg, so it's not neutral.
Compare your new switch with the one you're replacing to find the corresponding locations for the electrical screw connectors. Because the power is off, you can match up the connectors the easy way: Instead of disconnecting all the wires at once and possibly getting confused, unscrew and connect one wire at a time.
Attach the first wire you unscrew to the same-colored screw on the new switch as it was on the old; do the same with the second. To connect a wire to a terminal, strip off about 1/2 inch of insulation, using a wire stripper, and twist the end into a clockwise loop with long-nose pliers. The loop must wrap at least two-thirds but no more than three-quarters of the way around the terminal screw. Hook the wire clockwise around the screw so when you tighten the screw with a screwdriver, the clockwise force of the tightening screw makes the loop wrap tighter around the screw.
Gently push the new, wired switch back into the electrical box and screw it in place.
Screw on the switch plate and turn on the power.
Replacing three-way light switches
A three-way switch is a handy convenience to control a light from two locations, such as at the top and bottom of a staircase. If the words On and Off aren't embossed on the switch and it's one of two switches that control a single light or receptacle, you have a three-way switch. Seems like it should be called a two-way switch, right? The name refers to the fact that these switches have three terminal screws.
To replace a three-way switch, follow these steps:
Turn off the power to the switch at the circuit or fuse panel.
Unscrew and remove the switch plate; then use a voltage tester to make sure that the circuit is dead.
Unscrew the switch from the electrical box and pull it out with the wires still attached.
A three-way switch has at least three wires, and possibly four, depending on whether it has a ground wire. Two wires attach to brass screw terminals, which are usually at the top of the switch, and an additional wire attaches to a dark-colored (not green) screw terminal, which is usually at the bottom of the switch. Mark this third wire with a piece of tape and mark the wire on the same side of the switch directly above it with a piece of different-colored tape.
The new switch may have the electrical screw connectors in slightly different locations than the switch you're replacing. Most switches have a pair of terminals on opposite sides of the switch top and a single terminal at the bottom.
Remove the wires from the switch.
Attach the tagged wires to the corresponding terminals of the new switch.
Alternatively, you may choose to transfer one wire at a time from the old switch to the new switch.
If the existing switch has a green ground wire, attach the wire to the green screw terminal on the new switch or to the electrical box.
Push the new, wired switch back into the electrical box and screw it in place.
Screw on the switch plate and turn on the power.
