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Issues wiring upstairs/down stairs light switches

SeanMack

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Joined
Sep 29, 2025
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2
Hey everyone, hopefully someone can help.

I'm helping decorating my buddies place and am changing over some light switches. Its a double light switch at the top and bottom of the stairs and a single light at the top and bottom of the staircase.

The house is an older style council build. I'm totally stuck - I asked chat GPT for help but its running me in circles. the old switches were already removed so I couldn't see the old layout.

The down stairs light socket has 2 sets of live, neutral and earth (red black and earth) showing - a spare yellow cable and a spare red.

The upstairs has the same 2 sets of live, neutral and earth and another yellow cable.

I tested the cables on my voltmeter and the downstairs spare red is the constant live feed.

When I connected the permanent live to the downstairs yellow wire the downstairs light comes on.

I connected the downstairs live to the live on one of the 2 wire sets to send a current upstairs and connected that to the upstairs yellow wire and the upstairs light came on - so i can confirm each switches yellow cable takes current to the light.

My knowledge at this point is a bit spotty on how to wire these back up - I have 2 double light switches both with COM1 COM2 L11 L12 L21 L22

I believe in the old set up there was a small bridging wire involved as I found one near the old removed switches.

can anyone point me in the right direction on how to wire this back up - i don't know if this set up is conventional as it was an older council build but it was working before with the prior set up.

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Honestly, since the old switches are gone and you’ve only got loose wires, I’d be cautious. 2-way stair switches are simple once you know which is live, which are strappers, and which feed the lamps... but with no reference, you’re guessing. If you mis-land the permanent live, you’ll either have a dead switch or a short. If you don’t have the exact council-wiring convention in front of you, I’d say call in a sparky to map it in ten minutes.
 
After some digging and diagnostics I've mapped all the cables and figured it out (took a few hours but I got there 😅)

Thanks for getting back to me though 👍
 
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