How To: Wire a Light Switch
Replacing a light switch is a simple task. Here's how to do it efficiently and safely.
Although it’s easy to wire a light switch, you need a basic understanding of home electricity in order to do the job safely. If you’ve never before worked with wiring, hire an electrician and ask to look over his shoulder. Once you’ve learned the procedure, you should find that it takes no more than 10 minutes to wire a light switch. No advanced tools are required, and the steps are identical whether you are replacing a damaged switch or swapping in an upgrade (for example, a dimmer).
It is vital to complete this first step correctly; skipping this part or doing it wrong could be fatal! Before you do anything else, ensure that no power is running along the circuit that you’ll be working on. That means going to the breaker box and switching off the breaker that controls the switch you intend to replace.
Once you are positive that power has been cut to this particular switch, unscrew the switch plate (most are secured with two small flathead screws), then unscrew the old switch from the wall (here, flat-head and Phillips-head screws are equally common). Carefully pull out the old switch but leave the wires connected for now.
Observe the layout of the wires. You should see two black wires, each connecting to a different screw on the right side of the switch. These are called terminal screws. You should also see a green wire, called a ground wire, which attaches to a screw on the lower-left side of the light switch.
Loosen the screws holding the terminal wires in place. Once done, free the terminal wires, using pliers if necessary to undo a tight coil. Likewise, free the ground wire. At this point, you should be able to remove the switch from the wall; if it makes your job any easier, go ahead and bend the dangling wires out of the way.
Examine the ends of the wires for evidence of fraying. Clip off any degraded portions with a multitool or wire cutters. Remember to leave about a half-inch of wire exposed on each length. Because electrical wires experience stress over time and can weaken with usage, you must ensure that when the wires are reattached to the replacement switch, any portion of the wire that makes contact with the screws is undamaged.
Use a multitool or pliers to bend each exposed wire into a round hook. Try to round those hooks tightly enough so they fit snugly around the curve of the screws on the replacement light switch.
Now attach the hooked ends of the wires to the new switch. Start with the black wires, connecting them to the terminal screws on the right side. Their hooks should be oriented in a clockwise position. Proceed to attach the green wire, the ground, to the screw on the left. You may find that needle-nose pliers, though not essential, can help keep the wires in place as you tighten each screw.
Protect the switch from fires by wrapping electrical tape around the body and the terminal screws. Finally, screw the switch back into the wall, replace the switch plate, and turn the circuit breaker back on. That’s it—you’re done. Now let the light shine on!