2 way switching problems

30 May 2008
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United Kingdom
Hall lights, will switch on from end A and off from B - but will not switch on from B if switch A is off. First 2 pics single gang switch B 2nd 2 pics three gang switch A

Switch B (Crabtree) has 2 cables servicing it - a 3 core and earth - Yellow, Blue and Red + Bare earth and a 2 core Black and Red. Switch not marked with common, L1 or L2. Red from 3 core into top hole (common?), Blue into what should be L1, Yellow into L2. Other cable Black into L1, Red into L2
Switch A the one on the right of the 3 gang as you look at it has 2 cables servicing it both 2 core Black and Red - one has the Black cut off. Red to common - Black cut off Black to L1 Red to L2 both from same cable.
Anything obvious here? Switch B not having Blue or Yellow wires has thrown me.
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Has it always been non-functional, or did you change something?

Your best approach might be to identify the conductors via a combination of physical tracing and the use of your multimeter to check continuity, and to use the meter to identify COM on the switches, and reconnect it properly.
It has been like this since we moved in 11 years ago. I have looked at it a couple of times and given up as it was not at all obvious how to sort it. There are 4 lights in the hallway, wall mounted uplighters. These were all removed recently to allow for replastering, the wiring all looked fine with no obvious joints. My multimeter skills have not been put to this sort of test - working with it on my motorcycle on a 12 volt circuit is as far as it has gone. I guess if I think about it I could turn the power off at the consumer unit, join some wires together, and do some continuity tests.
It is the fact the wires are different colours - I assumed there would be the same cable between the 2 switches.
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