How to Replace a Dimmer Switch

At the mains, turn off the power completely before commencing this task. Failure to do so may result in a serious accident. Make sure everyone at home is aware of the danger of turning the power back on while you are working. Turn on the light at the switch to make doubly sure there is no power flowing through it. The light should not turn on. Switch it off again.

Loosen the screws of the light faceplate and pull it out from the wall carefully. Ensure you leave sufficient room to undertake work on the back of it.

Take a look at the wiring and note how it appears to make your task easier later. If you can, taking a quick photo of the wiring layout with your phone will help. You should see one of two combinations of wiring depending on when the house was last wired: blue or black, which is neutral; and brown or red, which is live. Green and yellow represents the earth wire. Loosen and remove each of the screws holding each individual wire in place. If there is any obvious damage to the current wiring, cut off the damaged end of the wire and then strip back a little insulation to reveal the inner wire.

Take your new dimmer faceplate and connect each of the wires back in the same positions they were in on the previous faceplate.

Push the faceplate into place in the wall, while taking extreme care not to trap the wires between the faceplate and the wall. The screw it securely into place.

Switch the mains power back on and test to see if the light dims and brightens when the switch is twisted in opposite directions.