Hi all,

Any electricians in the house? Need some help with a two way switch that doesn't work right. The downstairs hall light has two switches, but if the upstairs switch is off, the downstairs switch does nothing.

It's wired with a single 3 core and earth upstairs with L1 Red L2 Blue and L3 Yellow.

Downstairs we have 4 x 2 core and earth cables on a twin dimmer that does and upstairs light and the troublesome hall light.

The downstairs part of the dimmer has cable A wired Black to C and Red to L2. Cable B has Black to C and Red to L2. Cable C has Black to L1 and Red to L1 of the upstairs switch. Cable D does the upstairs dimmer Black to C and Red to L2.

I guess there's some sort of junction box some where as the light has a single 3 core cable.

With the downstairs switch on and the upstairs switched on:

Upstairs: L1 L2 and L3 are live.
Downstairs: L2 is live
Light on

With the downstairs switch off and the upstairs switched off:

Upstairs: L3 and L1 is live
Downstairs: L2 L1 and C are live
Light off

With the downstairs switch off and the upstairs switched on:

Upstairs: L3 is live
Downstairs: L1 and C are live
Light off

With the downstairs switch on and the upstairs switched off:

Upstairs: L3 and L1 live
Downstairs: L3 and C are live.
Light off.

Does anyone has any tips other than stop dicking around and phone an electrician?

Thanks!
Jon

Hi, I'm trying to understand your setup but struggling a bit. Are you saying you have 2 dimmers controlling the same light? Normally you would only have one 2-way dimmer and a 2-way switch controlling the same light. You can get special dimmers which work a bit differently where one switch is the real dimmer and you can have remote controllers for it but I don't get the impression that's what you are meaning.

Maybe some photos of your dimmers/switches (front and back ideally) would help, or a sketch of the wiring.

I should mention, I'm not an electrician but I am an electronics engineer and am familiar with home electrics including 2-way switches and might be able to help. Failing that, perhaps if you can provide more details then someone else might be more likely to jump in.

Cheers,
Craig.

Sounds like he has a 2 way switch at top of stairs, and a 2 gang dimmer downstairs, 1 for hall and 1 for stairs- 1 of which is 2 way

Home electric is dead easy innit?

Go get a new switch and it will have a wiring diagram you can check against what you got...

But it sounds like the 2 way should do the stairs not the hall

Thanks for the replies so far. Yes it's a two gang two way dimmer downstairs and a two way switch upstairs.

So how is the troublesome hall light related to the stairs 2 way?

The hall light is the downstairs light that's connected to both switches.

Does the upstairs switch have an L4 connection or just L1,2,3? If it has L4 then it’s probably an intermediate switch.

Also, where do the blue and yellow wires go from this switch?

So can you only turn the stairs light on from downstairs?

Blue and yellow will be the straps and will run back to junction box. As whet he's described suggests no neutrals at switches

quote:

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Originally posted by daniel mason
Blue and yellow will be the straps and will run back to junction box. As whet he's described suggests no neutrals at switches

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That's exactly how a 2 way switch is wired
Live to l1 or l2. Switch live to the other. Then a link between the 2 commons and a pair of straps between the l1 +l2 terminals.
If wired junction box/conduit method then life to 1 common,switched live to the other common and a pair of straps between l1 + l2. Its simple stuff

quote:

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Originally posted by daniel masonIts simple stuff

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I'm at a total loss with the explanation. But pretty sure I could have it sorted in 10 minutes if I was there, and if I could see some pice I'd be able to explain

I guess I'll need to start tracing wires and find the junction box...

Thanks for your help so far