Light switch cross gang wiring

2 Nov 2013
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United Kingdom
Help needed please.

I replacing some light switches which I have done many times but not seen this setup before.

Basically I have 2 x 2 gang switches.

Switch 1 (by the front door) gang 1 controls outside the light, switch 1 gang two is the first in a two way switch for the hallway lights (2 pendants).

Switch 2 (at the bottom of the stairs) gang 1 is the second switch for the hallway lights, second gang is the first switch of the landing lights.

All as expected so far. However when I look at the rear plate of switch 1 by the front door I'm seeing something odd. L2(right) = RED, L2(left) YELLOW with a red sleeve so switched live. However the two L2's are connected to each other by a short red wire.

COM(right) has no wire. COM(left) RED wire.

L1(right) = RED, L1(left) = BLUE with RED sleeve and a YELLOW with a RED sleeve

Switch 2 at the bottom of the stairs, with the other switch for the hallway lights has COM = RED, L1 = BLUE with RED sleeve and L2 = YELLOW with RED sleeve.

What is happening is that either switch will turn on the hallway lights, but the opposite switch will not turn them off. Only the switch that turned the lights on will turn them off. The other gangs are doing what I expect e.g turning on the outside light, or the landing light.

Basically, I have tried moving the terminals around, but it makes no difference.

Any advice would be hugely appreciated!
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The link between L2s must be permanent live between gangs.
So somehow you have mixed this up.
Do you have a means of safely testing for voltage, as you need to confirm which core is permanently live, then we can configure from there.
Are you sure the description of the wires in the switch by the front door is correct?

You say you have 2 red wires in L1 and L2 on one side and nothing in the Common.

Then TWO yellows a blue and a red in the Common on the other switch???


HOW MANY switches have you changed already before you hit this problem?
Guys, thanks for replying so quickly. I've checked the switch by the front door again and no, I had not described it correctly. Sorry.

Also being colourblind my girlfriend (yes I've resorted to her checking my homework) has pointed out that some of the RED's are actually PINK!

So here is the correct description:

COM (left) = PINK
COM (right) = PINK
Bothe COM's are wired together with a short RED wire, not the L2s.

L1 (left) YELLOW with RED Sleeve + BLUE with RED sleeve
L2 (left) YELLOW with RED Sleeve

L1 (right) no wire
L2 (right) RED.

So the right hand gang is for the outside light which works fine. I must have done something stupid with the other one!

As for your question re being able to test the wires for current, no I don't have any tools/kit for that. Are they expensive/difficult to use?

Thanks for your help guys.
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The link between the two commons makes no sense and you have an extra yellow.

Are there any other wires which are not used?

It would make more sense if the link wire was between Right com and Left L2 but without testing it is impossible to say.
Some observations

1: You mention "pink wires". These are almost certainly red wires that have either faded over time or were not coloured very well in the first place.
2: Wires usually come grouped in cables
3: You have mentioned three red wires, two yelllow wires and one blue wire.
4: Presense of yellow wires usually indicates 3+E cable one would therefore expect the same number of blue wires as yellow wires

So based on this my conclusion would be that you most likely have the following setup.

A 3+E from the hallway lights carries permanent live to the switches on the red core, neutral on the blue core and switched live back to the hallway lights on the yellow core.
A T+E from the outside light carries switched live on the red core and
A second 3+E cable provides two way switching for the hallway lights.

If i'm right you should find a piece of terminal block behind the switch joining a blue core to a black core.

The misbehaviour you indicate is consistent with this configuration and the wiring you describe.

Move the link wire so it joins left com to right L2 and tell us if everything behaves correctly.
Guys, thank you.. It was the connector wire, I had connected the two COMs together but as you said it should have been COM (right) to L2 (left) which has fixed it perfectly.

Thank you very much, I now have a house full of new switches that actually work!

I would never have figured that out without your help.

Much appreciated.

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