DIY: How to Install Light Dimmer Switches

Light dimmer switches are toggle, rotary, or slide switches that make it possible to adjust the level of light emanating from the fixture controlled by that switch. You might want to dim the lights in the dining room for evening meals, but have bright illumination for a card game with friends. Bright bulbs in the bathroom are great for shaving or putting make-up on, but in the middle of the night when you stumble in for a glass of water, it’s nice to have soft lighting that won’t blind you. It takes just a screwdriver and a few easy steps to install a light dimmer switch and have adjustable illumination in any room!

Turn off the power. Never work with live electrical wires. You’ll need to flip the switch for the circuit breaker for that room, or in older houses, pull out the fuse.

Remove the light switch faceplate. Unscrew the faceplate from the wall using a screwdriver. Once removed, thread the screws back into the faceplate holes or use the faceplate as a tray for the screws. This way they won’t roll off a table or get lost in the carpet.

Unscrew the light switch assembly. You’ll want to use a screwdriver (many switches accommodate both slotted and Phillips styles) on the mounting screws that attach the switch to the junction box. Most dimmers come with new mounting screws so you don’t need to save these.

Gently pull assembly from wall. The wires attached from the house to the screw terminals on the side of the light switch will now be visible. Generally power is white and the ground wire is black, but wire colors can vary as shown in the accompanying photos. The important thing is to make note of what color wires are attached to which terminals on the existing light switch. On a single pole you’ll generally have two wires, and on a 3-way light switch there will be three wires. Write down the color and terminal position if you don’t think you can remember, or attach a small piece of masking tape marked with the terminal position to each wire.

Unscrew the light switch terminal screws. Loosen these screws just enough so that the wires slip free.

Attach the new light dimmer switch. Most new dimmer switches will be labeled “Up” to help you place the switch correctly. The dimmer power terminal may also be labeled. Attach the house wires to the new dimmer switch, sliding the connections behind the terminal screws in the exact way the old light switch was connected.

Tighten down the dimmer switch terminal screws enough to hold the wires in place. Tuck the wires back into the junction box followed by the new dimmer.

Adjust the light dimmer switch and attach the mounting screws. Generally the screws go through a slotted opening so that you can slide the dimmer switch around until it aligns properly. Turn the screws only a couple times, just enough to hold the dimmer switch in place.

Test the dimmer switch. Turn the main power back on and check to be sure the new light dimmer switch works properly. It’s wise to check the switch at this point so that there’s less to take apart if there’s a problem. Once it’s working, you can finish the installation.

Tighten the dimmer mounting screws. Reattach the old faceplate, or attach a new one if you’ve bought a different style switch. Thread in all the screws first to make sure the faceplate is aligned correctly, then tighten the screws. Your new light dimmer switch is installed and ready to use!