I am a complete DIY novice, and reading through past posts mean nothing to me, so I'm desperate for some very basic advice!!!
Our upstairs hall light can be controlled by a switch upstairs and downstairs, however we could only control the downstairs hall light downstairs. I'm hoping we will be able to do both from both upstairs and downstairs so I bought a double switch from Homebase. See pic of back. It's a bit dark (I've turned off the electricity!) but there are two holes that say COM and then two that are L1 and two L2.
I've also attached a picture of the wires coming out the wall. There are two red, a yellow and a black. All have brown tape wrapped around them OTHER than the two red wires.
I can see a yellow/green wire has been attached to the back of the box, and then disappears into the plaster (I'm not sure if this is bad plastering or meant to happen!?)
What colour wire goes into which of the COM, L1 or L2?
There is no standard colour code. Well there is line should be brown and neutral blue but no neutrals in a switch so all should be brown but that would be rare. So green/yellow is earth and is likely connected to back box.
The rest what ever colour are line. (Both line and neutral are considered live so what you may have called live I call line)
So assuming it was not originally two way. On the orignal switch the wires would have gone to Com and either L1 or L2 the other being left blank with no wire. On the new switch these two wires go to L1 and L2 (not Com) and then a three core and earth cable is taken between the two switches. Likely coloured Brown, Black and grey. Does not matter which wire goes to which terminal as long as it goes to same terminal on both switches. So if brown goes to com on one switch it must also go to com on the other switch. Well really only the com is important if you swap L1 and L2 the switch just works the other way but still works.
If it was already two way then look at other switch and copy the connections. One switch will have one wire in each hole the other will have two wires in L1 and L2 and just one wire in the com.
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