Replacing light switch with dimmer

[lordy100]

Hi, I'm a complete novice so apolgise in advance for my stupidity, just don't want to risk anything with electrics involved!

I have recently had a bedroom re-plastered, and decided to get new switch for light, replacing the old plastic one with a new metal dimmer switch. Unscrewing from the wall, I've discovered two wires attached to switch - a red and a black - but in the instructions with the dimmer it is looking for three wires. If it helps I think it is the earth that is missing. Help what do I need to do?

 

[Spark123]

If there is no earth present you can only install a double insulated dimmer switch i.e. a plastic one.

 

[breezer]

what terminals have you on the switch? (it may be a 2 way, which is fine)