Electrical light switch wiring instructions and help

By following these basic steps, you can easily wire a light switch in your home. If you encounter problems, try the following troubleshooting guide.

Photo Credit: Shaun Cammack
By Tara Gilbert

Wiring a light switch is a simple do-it-yourself project whether you are replacing an old light switch or adding a new one. By observing some basic safety rules, you can easily complete this project in less than an hour. The following steps will guide you through the process, as well as provide some suggestions in case you have problems with your light switch.

Installing A Light Switch

1. Turn off the power at the fuse box. – Before you begin working with the wires for the light switch, turn off the power to the circuit at the fuse box. Once the power is off, remove the cover plate and test the wires with a circuit tester to be sure that no power is running through the lines.

2. Remove the old light switch. – If you are replacing an old light switch, unscrew it from the electrical box. Next, remove the wires that are attached to the switch’s terminals.

3. Double-check the wires. – Wires that are broken or nicked will not provide a solid connection to your new light switch. To avoid problems with the connection, trim damaged wires and strip the sheathing from the wire so there is 1 inch of bare wire.

4. Attach the wires to the terminal. – If your light switch is at the end of the circuit, there should only be three wires in the electrical box, one green, one white and one black. Attach the green wire’s 1 inch bare end to the green grounding screw in the electrical box. Tighten the screw to secure it in place. Next, attach the white wire and the black wire to the proper terminal. Make sure they are screwed securely in place but not too excessively tight.

If your light switch is in the middle of the circuit, then there will be two sets of wires for each color. When you wire your light switch, you will connect the two green grounding wires and a third short piece of grounding wire with a wire connector. Next, attach the short piece of grounding wire to the electrical box’s green grounding screw. Also join the white wires with a wire connector. Attach a black wire to each terminal.

5. Secure the switch and cover it. – Gently tuck the wires into the electrical box and screw the switch into place. Then place the coverplate over the switch and screw it into place.

6. Test the switch. – Once the switch is installed, turn the circuit back on. Turn the switch on and enjoy your finished project.

Troubleshooting

If your light switch does not appear to be working, try these steps.

1. Check for loose connections. – Loose wire connections cause the most switch problems. Check to see that the wires are securely attached to the switch. The screws tightened enough to keep the wires securely in place.

2. Examine the ends of the wires. – Wires that are frayed, bent or nicked sometimes will not provide a good connection. Trim the ends of the wires and strip the plastic sheath until 1 inch of wire is showing and reattach the wires.

3. Make sure bare wire is not touching the electrical box. – Bare wires that touch the electrical box will trip the circuit breaker or blow a fuse. If this is the problem, check to make sure wires have enough plastic sheathing to protect them.

4. Replace the switch. – Switches, like other mechanical parts, will break. Over time, parts will wear out in the switch, so you will need to replace the entire switch. You also need to be sure you have the correct switch for the circuit. If you replaced a switch, make sure it has the same number of terminals, screws, as the original.