Struggling to figure out how to wire a 3-gang light switch

[spleenharv]

Hi everyone,

I've worked with low voltage electronics now but I'm trying to sort some electrical issues with my new house. I'm in the UK with 230V AC.

One problem has stumped me in particular, which is how to wire a 3-gang light switch with 3 separate lights. With the old wiring both of the existing lights worked, but the new light (a 2-wire porch light) did not work. I did eventually manage to get the new light to work, but switching it on would trip the circuit breaker for the existing lights.

The diagram below shows the colours of the wires that are coming out of the back box that correspond to each light. The house is a mixture of pre-2004 and post-2004 wiring so I'm not entirely confident in identifying which wire is which except for earth. For example I'm not sure what the yellow wire is for on one of the existing lights.

If someone could tell me how to wire this I'd really appreciate it, I've been tearing my hair out trying to figure it out.

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[dick_freebird]

It's been my experience that you're better off pulling fresh
wire that you know, than trying to deduce what previous
owners or workmen have left you.

If one more light is popping a breaker, either you've got
too much on that branch for the rating, already, or you
have added a wiring fault.

In that vein I'd suggest removing the bulbs that were good
before you started, and see if the breaker's still popping.
That would indicate a fault instead of an overload.

All those colors? Creepy. Here in the States you see only a
few and they have meaning (black and red for the two hot
phases, white for neutral). If I found blue, yellow, orange,
I'd suspect somebody before me had no idea what they
were (or should have been) doing.

 

[spleenharv]

Cheers - unfortunately I have no idea how to lay new wire in!

Pretty sure I have the live wires correct - red wires are both hot and have continuity to each other, so I have placed the porch light (blue/brown wires going to bottom switch in pic) from L1 hot to L1 porch light switch. Problem is I have no idea where to wire COM to. If I wire it to the black wire (COM of middle switch) nothing happens. If I wire it to the yellow wire or the other blue wire (COM of upper switch in pic) the RCCB trips. I've tested the wiring of the porch light and it is OK, no shorts and the bulb is working in another socket.

Am I SOL without laying down more wiring? What wiring would I need to add?

 

[sparkyuk]

Cheers - unfortunately I have no idea how to lay new wire in!

Pretty sure I have the live wires correct - red wires are both hot and have continuity to each other, so I have placed the porch light (blue/brown wires going to bottom switch in pic) from L1 hot to L1 porch light switch. Problem is I have no idea where to wire COM to. If I wire it to the black wire (COM of middle switch) nothing happens. If I wire it to the yellow wire or the other blue wire (COM of upper switch in pic) the RCCB trips. I've tested the wiring of the porch light and it is OK, no shorts and the bulb is working in another socket.

Am I SOL without laying down more wiring? What wiring would I need to add?

reds in common, brown cable going to light in terminal 1 on switch, join blue and black cables together