Yet another hall / landing question!

[nleaney]

I was trying to replace a security time light switch at the top of my stairs. Photographed the switch I was replacing and thought I'd simply be able to match the wiring but how wrong could I be!

While I'm trying to get this all working I'm just using a regular 2-way switch. Once I have got everything working as it should I'll try the electronic timer again.

Upstairs is a single, 2 way switch to control the upstairs light. Downstairs theirs a three gange 2 way switch for the outside light, downstairs lights and upstairs light.

The strange thing is that the wiring for the downstairs switch is only one way. This switch hasn;t been touched (by me!) so I'm confident it was as supplied when the house was built and everything worked then! Into the downstairs switch is a white sheathed red/blue/yellow (+ earth) cable. Blue is in Common, Red in L1 and Yellow is disconnected.

Upstairs I have a the same white sheathed red/blue/yellow (+ earth) cable as well as a grey sheathed twin red (+ earth) cable.

I can get the upstairs light to work if I connect the twin red cable across Common and L1. Can't seem to work out how to get any response from the downstairs light though and from what I have read elsewhere, it seems odd that its not using a 3 core connection anyway?

Any step by step fault finding instructions would be greatly received. I thought I knew about this stuff but this has seemingly got me stumped at the moment!

Thanks

 

[nleaney]

Answered my own question (kind of)

Given that I have a three core cable running from downstairs to up, I decided to wire the switches as per the helpful diagram I found diyhowto.co.uk rather than spend any more time trying to fathom how it might have ever worked before!

Everything working with the normal switch so swapped it out for a TimeGuard ZV700 and (after adding the optional FL1 across the lamp to stop my low voltage bulb flickering when 'off') everything seems fine.