How to Replace a Light Switch

Most DIYers shy away from doing electrical work for fear of getting shocked or causing a fire. And that’s certainly understandable; electricity is not to be trifled with. However, there are many simple electrical upgrades that, when done correctly, are perfectly safe. And few electrical projects are as simple and safe as replacing an old light switch.

If you have wall switches that are old and badly faded, cracked, or just worn out and ugly, then replace them with brand-new switches. The swap-out takes less than 15 minutes and a new single-pole light switch costs less than a buck, making it one of the most affordable upgrades ever.

Safety First

The most important rule about electrical work is that you absolutely must turn off the electricity to the circuit that you’re working on.

⚠️: Working on a live electrical circuit can cause serious injury or death.

Go to the main electrical panel and flip off the circuit breaker that’s feeding power to the light switch. (Or, unscrew the fuse if your home has a fuse box.) Next, remove the cover plate from the switch and use a non-contact voltage tester to confirm that the power is indeed off.

Touch the tester’s probe to the wires on the switch. If the electricity is off, the tester will not light up or emit an audible beep. However, if the tester lights up or beeps, then the power is not off. Go back to the electrical panel and identify and turn off the correct circuit breaker (or remove the right fuse).

Now, unscrew the switch from the box and pull it forward. Use the tester to check for any other live wires inside the box. Every conductor (electrical wire) in the box should be dead. Once you’ve confirmed that the power is off to all the wires inside the box, you can proceed.

💡 Use your cell phone to take a photo of how the switch is wired. That way, you’ll be sure to reconnect the wires correctly to the new switch.

If you can’t kill the electricity, the switch box might be connected to a cable from a different circuit. It’s not a common problem, but with old houses, anything’s possible. Have the wiring and circuits checked by a licensed electrician.

Get Started

Once the electricity is definitely turned off, use a screwdriver to loosen each screw terminal and remove the hooked wires from beneath the screw heads.

If the wires aren’t tightened under screw terminals, but instead are pushed into holes in the back of the switch, here’s how to release the wires: Look for a small square hole directly below where each wire goes into the back of the switch. Firmly press a narrow slotted screwdriver or nail set into the square hole while simultaneously pulling on the wire until it releases from the switch.

Once you’ve disconnected all the wires, bend them out of the way and remove and discard the old switch. Use a vacuum to clean the box of all dust and dirt.

Snip and Strip

Check the ends of the wires for nicks, cracks or rough spots. Wires expand and contract slightly every time the power is turned on and off, and they can eventually fail at these stress points. Snip off the damaged section of wire and use wire strippers to strip off about 1/2 in. of insulation, exposing new, clean wire.

Bend a Hook

If you plan to connect the wires to screw terminals on the new switch, bend a rounded hook onto the end of each wire using either needle-nose pliers or the hole at the tip of the wire stripper.

If using the push-in connectors at the rear of the switch, strip off 1/2 in. of insulation and leave the wire ends perfectly straight.

Attach the Wires

Position the switch in the electrical box so that the ON position is facing up toward the ceiling. You don’t want to install the switch upside down. Next, refer to the switch-wiring photo you took earlier to connect the existing wires to the new switch.

Here’s how a single-pole switch is typically wired: The electrical box usually has two two-wire cables coming into it. Each cable has a black insulated wire, white insulated wire, and bare copper wire. Start by using a twist-on wire connector—commonly called a Wire Nut—to join together the two white insulated wires. Fold and tuck the white wires into the back of the box; they’re not necessary for operating the switch.

Next, twist together the two bare copper wires, leaving about 4 inches of each wire not twisted. Snip off and discard one of the 4-in. wires. Take a green grounding connector—the kind with a hole in its cap—slip it over the remaining 4 in. wire, slide it down and tightly twist it onto the two bare copper wires. Bend a hook onto the end of the copper wire, wrap it clockwise around the switch’s green grounding screw, and tighten the screw.

Now, take one of the black wires, bend a hook onto its end and connect it to one of the bronze screw terminals on the side of the switch. Take the second black wire and connect it to the remaining bronze screw terminal. Alternatively, if there are push-in terminals on the back of the switch, you can use those to connect the black wires. One of the black wires will bring power to the switch, the other will energize the light fixture; this is commonly referred to as, power in and power out.

Install the New Switch

If the electrical box is made of plastic, as most are these days, carefully fold and push the wires into the box, as you press the switch flat against the face of the box. Secure the switch with two mounting screws, then install the cover plate.

If the electrical box is made of metal, be sure to protect the wires from contacting the metal box and possibly shorting out. After making all the wire connections, wrap electrical tape all the way around the switch body, covering the live screw terminals and shielding them from the metal box. Screw the switch to the box and install the cover plate.

Restore power to the switch by flipping on the circuit breaker (or replacing the fuse). Then, one the last step: Flip the switch on and off to confirm that you’ve wired it correctly, and it’s operating properly.