How to replace a light switch
You will need:
- Replacement switch plate or dimmer switch
- Small and medium electrical screwdrivers
- Voltage tester/meter
IMPORTANT NOTE: Before unscrewing your switch plate, you must make sure the lighting circuit is isolated at your consumer unit.
Take out the relevant fuse and keep it in your pocket, or switch off the circuit breaker and ensure no one can switch it back on.
After unscrewing your switch plate, use your voltage meter to ensure that there is no current flowing through the wires you are using. First make sure your voltage meter is working, too.
Here's a guide to voltage testers. If you find any current flowing with the consumer unit switched off, rescrew your switchplate up, and call in an electrician immediately.
You should read our DIY glossary: Electrics, before getting started.
If you decide to fit a dimmer switch on a standard light switch, and after isolating the supply as above, undo the existing plate and check the wiring layout. Then draw a diagram of where all the wires go and the wires' colour. Also put a masking tape tag on each wire, saying in which port the wire is fitted... for example, C, or L1.
Take note of any short plastic sleeves or tape fitted over existing wires, too.
Then take this along to the store and talk to a member of staff to make sure the new dimmer will work with your wiring.
In most cases, the new dimmer will be wired in exactly the same way as a normal replacement plate. If you cannot get a dimmer switch to match your existing wiring, call in an electrician.
Warning: You must not replace a pullcord switch in a bathroom with a wall-mounted light switch. Never fit a dimmer switch to a flourescent tube.
For more information see the Electrical Contractors Association.
Tip: This step-by-step guide is for replacing a simple plastic single switch, like for like. For more complicated jobs, you need to call in an electrician.
If you are fitting metal switch plates, these have to be earthed to the mounting box at the back. If you do not know how to do this, call in an electrician.
Step 1: Unscrewing the plate
Use a small screwdriver to undo the two screws holding the switch plate onto the mounting box in the wall. And check again that the switch has been isolated with your voltage meter.
Step 2: Changing the plate
Single switches are wired to the ring circuit by two core cables and and an earth cable, which will be screwed to the mounting box that is housed in the wall.
Once you've removed the switch, draw a diagram marking up which coloured cables go in which terminals in the switch and back plate. The terminals in the switchplate will have names, such as C and L1.
You may want to put masking tape tags on the wires too, saying in which terminal the wires are screwed.
Next, unscrew the small screws in the terminals, remove the wires and then connect them to the new switch plate terminals, fixing the wires in the same terminals in the new plate, as in the old.
Make sure the wires are tightly screwed in place, and that there is no bare wire visible for all of the wires.
You can leave the earth wire screwed to the mounting box. However, if there is no green and yellow sleeving around the earth wire, make sure you fit some before continuing.
Step 3: Finishing
Make sure the wires are all firmly secured and bend any extra sheathed cable neatly into the box so that it cannot be trapped by the new cover plate.
Screw the new cover plate onto the wall box and then reconnect the supply.
Check the light works.
If you have followed these instructions, and your light doesn't work, and you've checked the consumer unit, then islolate the lighting circuit again, and call in an electrician.