Light Switch Fun!

[Dan_129]

Just moved into a new (old) house and wiring in hall/landing light switch at bottom of stairs. There was no switch, just wires, when we arrived.
Problem is there are 3 cables entering the box, all with red wires. The first has a single red, the other two have 2 red and one earth. Does anyone know what the likely wiring for the switch? Thanks

 

[Deryck Tintagel]

Questions:

what is the wiring at the landing switch - is it similar? With an extra cable with two reds?
Does the landing light work without the switch downstairs?

There are two things I can think of from the top of my head but the answers to the question will be a pointer.

 

[ban-all-sheds]

Do you have any means of identifying live wires?

 

[securespark]

Souns like it could be a two gang switch with a single as common of a two-way (landing light plus one of the other pairs as the L1 & L2 and the other pair as a one-way (hall?).

But as Ban says, get a voltage tester (pref non-contact - MK Powertracer is good from all DIY sheds) and try to id which wires are live.

 

[Deryck Tintagel]

I've just re-read the original posting - didn't read the bit about 2 twin red cables.

I agree with Securespark - just need to identify which twin red belongs to the single red in the two-way switch. Have a look at the landing light switch for a clue: where does the single red connect - I would hazard a guess at the COM terminal. There should be two twin red cables connected to the L1 and L2 terminals. If so then ...

With the mains OFF (upstairs and downstairs MCBs off just to be sure that all wires are dead) you could connect the twin reds of one cable together in a terminal block and insulate all others individually.

Turn on the MCBs and see which light operates - if it is the Hall light then connect this pair to COM and L1 of one side of a two-gang two-way switch. If it is the landing light then connect this pair to L1 and L2 of the second two-way switch and the single red to the COM terminal. All with the mains off of course.