Replacing a damaged switch is a matter of connecting the existing wiring to the terminals of the new switch so  that it is connected in exactly the same way as it was in the old one. Always turn off the power and remove the fuse before you take off the face plate to inspect the wiring. In the case of a surface mounted switch, make sure that a new face plate will fit the existing box otherwise you will have to replace both parts of the switch.

If you are able to use the old box, use the old machine screws when you attach the new face plate. You can then be certain of having screws that will match the old threads. If you want to replace a surface -mounted switch with flush-mounted one, remove the old switch, then hold the metal box over the position of the original switch and trace round it. Cut away the plaster to the depth of the box and screw it to the brickwork. Take great care not to damage the existing wiring while you are working.

Replacing a One-way switch

If you look at a one-way switch, you will find that it is serviced by two core and earth cable. The earth conductor if there is one, will be connected to an earth terminal on the mounting box; and the red and black conductor will be connected to the switch itself. A true one-way switch has only two terminals, one situated above the other, and the red or black conductors can be connected to either terminal.

  1. The back of the face plate is marked ‘top’ to ensure that you mount the switch the right way up, so the rocker is depressed when the light is on. The switch could work just as well upside down but the up for off convention is useful one, as it tells you whether the switch is on of off even when the bulb has failed.

Replacing a two-way switch

A two-way switch will have at least one conductor in each of it’s three terminals. Without going in to the complexities of two-way wiring at this stage, the most straight forward method of replacing a damaged two-way switch is to make a written note of which conductors run to which terminals before disconnecting the various wires. Another way is to detach the wires from their terminals one at a time, then connect each one to the corresponding terminal on the new two way switch before dealing with the next conductor.