Light Switch - Replacing

Selecting a replacement light switch

If a switch needs to be replaced, because it is damaged or you require one of a different style, be sure to buy one with the same function. For example two gang, two way. For more information on the types of switch available see our Light Switches article. Also, make sure with a surface mounted switch that it matches the profile of the mounting box. If not, you will need to buy a suitable box as well.

Removing the old light switch

1. Switch off the power at the consumer unit for the circuit concerned. If you have removable fuses at your consumer unit, switch off the power at the consumer unit and remove the fuse for this circuit.

2. Release the faceplate retaining screws and ease the switch away from the wall so that you can access the terminal connections on the back of the switch.

3. It is essential that the new switch is wired up in the same way as the old one. This will be straightforward enough if you have a single gang one way type, but those with several switches and/or ways, will have many wires which can be confusing.

Identifying the wires or cables

4. The simplest way is either to label each conductor with the location of the terminal to which it connects, or to transfer one conductor at a time to the corresponding terminal on the new switch.

5. Labelling the conductors first before removing them is the easiest method. Once they are labelled, use a small flat bladed screwdriver to release each of the terminal connections and remove the conductors.

6. Earth conductors will not need to be labelled as they all go to the same connection terminal. This may be at the back of the box or, in the case of a metal switch, a terminal provided at the back of the switch plate.

7. If you have more than one gang or switch, be sure to label each set of conductors according to the gang they are connected to as well. With a two gang one way switch for example you would have:

A ‘C’ – common on gang A
A ‘L1’- Live back to the light on gang A
B ‘C’ – common on gang B
B ‘L1’- Live back to the light on gang B

Connecting the new light switch

8. Take the new light switch and slacken the connection terminal screws ready.

9. Check each of the conductors ensuring that none are damaged.

10. Reconnect the labelled conductors to exactly match the original wiring.

11. In this example we have a two gang one way switch, and therefore two sets of conductors to deal with. We have a Common, and an L1 for each of our switches (or gangs) A and B

12. Insert the conductor labelled ‘B L1’ into the corresponding terminal on the back of the switch (or gang) B

13. Tighten the connection terminal screw to secure this conductor and ensure that it is fully housed and there is no exposed conductor showing. Remove the label.

14. Insert the conductor labelled ‘B Common’ into the corresponding terminal on the back of the same gang. Remove the label.

15. Repeat the process for the other conductors connecting them to the appropriately labelled terminals of the other switch (or gang) A.

16. As mentioned earlier, you may have more conductors but follow the process of connecting corresponding labelled conductors to their appropriate terminals.

17. Once all conductors have been inserted into their appropriate connection terminal on the back of the light switch, and all have been properly secured, double check your wiring and connections.

18. Carefully push the light switch back to the back box, gently folding the cables as you go, so that they sit neatly into the box.

19. Fasten the switch to the box with the retaining screws. Tighten the screws alternately to draw the switch back evenly.

20. As you tighten the screws, hold a small spirit level against the top of the switch to ensure it is level. The screw mountings will allow for a small amount of vertical adjustment.

21. Once you are sure that all work has been completed correctly, switch the power back on at the consumer unit. In the case of removable fuses, replace the fuse for the circuit, and switch the power back on. Check that your light switch is working correctly.