DIY Doctor UK DIY Forums

I am in the process of changing light switches in my house, the double switch in the hall controls a single switch and light at the top of the stairs and the light in the hall. When removing the cover I find the new switch is not the same as the old. The old cover has L1, L2, and Comm at the top, and the same at the bottom. The new cover has 2 Comms at the top and L1 and L2 twice at the bottom. The Wiring is Yellow, Red and Blue from 1 cable and 2 Red wires from the other cable. Which wires do I attach to which terminals.
Vic Cohen

The C or Common is the important terminal. If you get L1 and L2 swapped it will mean switch works wrong way but it will still work.

So make careful note of which wire with three core goes to C on old switch and make sure it goes to C on new switch.

With two reds then one on C and other on L1 and getting them wrong would not really matter. If switch works wrong way swap to L2.