3 Gang switch with lots of wires

11 Mar 2010
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United Kingdom
I was taking a 1 gang and seperate 2 gang switch from their poor positioning and combining in the sensible place in a nice neat 3 gang switch. Unfortunately only one circuit works if I re-wire them exactly as they were, as below.

Earth = 3green&yellow with 3 copper wires in each, currently all connected to the box

Black = In their original groupings in two of their seperate housings (like legos peices.)
3 black + 1 blue in one
2 Black in the other

Switch 1 = 1 Yellow (com), 2 Reds (L1), 1 red + 1 Blue (L2)
Switch 2 = 1 Red (com), 1 Red (L1), 1 Red (L2)
Switch 3 = 1 Yellow (com), 1 Red + 1 Blue (L1), 1 Red (L2)

In this configuration I think it's Switch 3 is the only one that works. How SHOULD it be wired?
I basically want the "room switch", "landing switch", and "stair switch" to turn on&off their respective lights seperately.

Thanks in advance
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Are you certain the reds were wired like that in switch two?

Is switch 2 by any chance the room?

It may be that L2 should be left empty; and two reds go in L1 or com
and another red in the remaining L1 or com.

In other words this switch may be one way ie no other switches turn pn the light.

You need to confirm which switches do which rooms.
Also need to know how many lighting circuits are connected to this switch
ie do you need to isolate more than one fuse or breaker at the mains?
Unfortunately only one circuit works if I re-wire them exactly as they were, as below.
Now you know that can't be quite true, can it?

Unless only one circuit was working beforehand, then if you have rewired things exactly as they were then everything will work exactly as it did.

What steps did you take to ensure that you kept track of which conductors were in which cable?

Have you taken note of any changes in orientation of the COM/L1/L2 groups from one switch to another? Sometimes they are laid out in alternately inverted triangles, sometimes all the same way up.

I count 18 conductors in your description, but after accounting for 2x3C+E cables you've got 1 blue left over (and no brown), and 5 blacks but 6 reds.

How many cables have you got, and what are they?
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To get the wiring to this one new position did you have to extend or replace any of the old cables?

If so, tell us how.
Before I get into answers, let me point out the stairwell light won't come on even if it's the only circuit wired in, & that set I'm 100% certain I have wired as they were (I've checked the bulb.) However it's also the only light that can be turned on at another location (which doesn't work either.)

Ok, answers in reverse.

1) I replaced/extended no cables, although I may need to extend one of them.
2) Switch 1; works the stair light and also has a 2nd switch at the bottom of the stairs
Switch 2; works spotlights in the room
Switch 3; works a central light & fan in the room
(admitedly I could have switch 2 & 3 the wrong way round, but surely they should still turn ON?)

1) To keep track, I marked the cables themselves before I disconnected them, with regards to "com", "1", & "2"
2) Yes I paid attention to orientation as they did swap like you said.
3) I have 3 blues total (one is in with the blacks)
4) I have 4 cables I think... I'll take everything out again and see if I can't sort out the mess left behind for in regards to which cables to feed what.
Ok I found an extra yellow & red that had got lost in the wall, so hopefully the other room lights should now work.

HOWEVER, that still doesn't explain the stair light, (Switch 1), or why it won't switch on from the 2nd switch either.

I may be able to get a photo today now there's some daylight, but to clarify the CABLES for the stair light, consists of 3 cables.
1 has; 1 yellow (com), 1 red (L1), 1 blue (L2) & 1 earth
2 has; 1 red (L2), 1 black (terminal block) & 1 earth
3 has; 1 red (L1), 1 black (terminal block) & 1 earth

ps.I tried wiring it to a different gang to check it wasn't that at fault, but no joy. So that's Gang & Bulb tested, & it's on the same fuse.

Thank for all your help!
if you had wired it correctly it would work.

take some pictures of the wiring, including sheaths.

you are going to need a multimeter too
It was definately wired "right" (as it was, and it did work before)

I'll take a picture, but is there anything other than bulb or fuse that could cause that one light not to work?
It can only be the competence of the person doing the work ;)

Uh Oh, I'm in trouble then :)

Well good news is everything seems to magically be working again now,
bad news is I have no idea why.

I wired in the extra yellow and red that had been missing behind the box, which aren't wired to the stairs at all, but now they all seem to be working.

Thank you for the swift and helpfull advice from everyone :)

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