How to Replace a Light Switch

Go to your home's main electrical panel and flip the breaker that controls the light switch to the OFF position. If your breakers are not clearly labeled, leave the light turned on and flip breakers one at a time until the light goes off — that is the correct one. Put a piece of painter's tape over the breaker so nobody restores power while you work. Return to the switch and use a non-contact voltage tester in the next step to confirm the circuit is truly dead.

Hold a non-contact voltage tester near the switch body and the wall plate screws. It should stay silent and dark. Then — just to be sure — unscrew the wall plate, remove the two mounting screws holding the switch to the box, and gently pull the switch out about an inch so you can touch the tip of the voltage tester to each wire terminal. If the tester beeps or lights up on any wire, stop and find the correct breaker. A $10-15 tester is cheap insurance against a 120V shock.

Pull the switch the rest of the way out of the box, letting the still-connected wires come with it. Before disconnecting anything, take a clear, well-lit photo of the wiring with your phone — capture which wire goes to which screw terminal. For a single-pole switch you should see two hot wires (usually both black, sometimes one black and one other color) on the two brass screws, and a bare copper or green-insulated ground wire on the green screw. If you see more than 2 hot wires or a red wire, stop — you likely have a 3-way switch and need to buy a 3-way replacement instead.

Loosen each of the two brass screw terminals counterclockwise until the wire loop slips free. If the wires are backstabbed instead, insert a small flat-head screwdriver into the release slot next to each wire and pull the wire straight out while pressing in on the release. Disconnect the ground wire last. Straighten any kinked wire ends with needle-nose pliers, and inspect the exposed copper — if it is nicked, corroded, or shorter than about 3/4 inch, strip back fresh insulation with wire strippers to expose a clean 3/4-inch length of bright copper.

Start with the bare copper or green-insulated ground wire. Using needle-nose pliers, form a clockwise hook at the end of the wire — clockwise so that tightening the screw pulls the loop closed rather than pushing it open. Hook the loop around the green grounding screw on the new switch and tighten the screw firmly until the wire is clamped with no loose copper sticking out past the screw head. If the electrical box is metal and has its own grounding pigtail, twist both grounds together with the new switch's green pigtail (if your switch has one) inside a wire nut.

The two hot wires go to the two brass (gold-colored) screws on the side of the switch. On a single-pole switch, the two brass screws are interchangeable — it does not matter which wire goes on top and which on bottom. Form a clockwise hook on each wire end with needle-nose pliers, hook each wire around one brass screw, and tighten firmly. Tug gently on each wire after tightening to confirm the connection is mechanically secure. Wrap one turn of electrical tape around the body of the switch, covering the screw terminals on both sides — this prevents accidental contact with the metal box.

Carefully fold the wires in an accordion pattern and push the switch back into the box — do not cram the wires in, as sharp kinks can damage the insulation. Align the switch mounting tabs with the screw holes in the box and drive the two Phillips-head mounting screws until the switch sits flush with the wall surface. Use the long slots in the mounting tabs to adjust the switch until it sits perfectly level (important for matching the final wall plate). Snap or screw the wall plate into place — it should sit flat against the wall with no gaps.