How to Install 3-Way Light Dimmer Switches

A three-way dimmer switch allows you to control a light fixture from two or more locations. This type of dimmer can be installed in existing three-way-controlled locations by replacing one of the on/off light switches for the light fixture. Dimming a light fixture allows you to save energy and create mood lighting by decreasing the bulb wattage to lower than the indicated wattage stamped on the bulb. Replacing a light switch with a dimmer is a fairly easy procedure that should take less than one hour.

Installing dimmer light switches is quick and fairly simple.
  1. Turn off the power to the circuit you will be working on by flipping the switch on the circuit breaker in the electrical box to the off position.

  2. Remove the plastic cover plate from the switch at the location you want to install the dimmer by backing out the holding screws with a flat-blade screwdriver in a counterclockwise direction.

  3. Test the wires to make sure the current has been turned off by holding a no-contact electrical tester close to the wires. If the tester beeps, the current has not been turned off.

  4. Back out the screws that hold the switch to the electrical box with a Phillips screw driver in a counterclockwise direction. Pull the switch out of the electrical box and loosen the screws holding the wires with a Phillips screwdriver in a counterclockwise direction. Use a small piece of masking tape and label the common wire attached to the odd or differently colored screw. Remove the wires from the switch and set the switch aside.

  5. Install the wires to the new dimmer switch by wrapping the bare ends of the wires around the screw posts, then tighten the screws by twisting them in a clockwise direction with a Phillips screwdriver. Make sure the labeled wire attaches to the common terminal on the switch. Match the white and black wires on the switch to the white wire and black wires from the electrical box. Attach the bare wire to the ground terminal on the switch.

  6. Carefully push the wiring and switch into the electrical box. Attach the switch to the box by turning the holding screws clockwise with a Phillips screwdriver. Replace the switch plate cover by tightening the holding screws with a flat-blade screwdriver, turning clockwise.

  7. Turn the power back on at the breaker box and test the switch by turning it on.