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I have replaced the light switches in my home with something a bit nicer. All has gone well with nobody getting electrocuted. I was, or thought I was, careful in wiring up the replacement switches in the same way as the switches I removed, but one is not playing ball. It is the hallway light that has two switches that control the light - one switch at each end of the hallway. Now since i've replaced the switches one switch will turn the light on and off, but other has no effect.
I've had a look at the wires at the back of the switch that works. If you think of the connections being Com and 1 & 2, then the Comm is permanent live (which I think is correct as this is the pole of the switch), one of the other terminals goes live when the light is on (seems correct to me) and the other is switched live by the other light switch. I thought about swapping the wires connected to the 1 & 2 terminals but thought i'd check before just sucking and seeing before I get into the guessing trial and error game. So if I swapped the wires connected to the 1 & 2 terminals would that have an effect or just result in no change?
I suspect it is the wiring in this switch which is the problem because as I removed the old light switch at this location some of the wires seemed to act like a spring and sprung out when I unscrewed the terminal so it is possible (probably) that a couple of the wires became switched before I took note of where they were all connected, so highly likely that I replaced them in the wrong order.
Cheers.
Fixed live shouldn't be going into the common on a 2 way switch. Look online for the wiring diagram for a 2 way switch should make it clear.
To understand 2 way switching circuits, you need to meditate and study the diagram, then get in the zone.
Beware, it's temporary, a few years ago, when renovating a house, I totally got it and could do it with ease. Now it's just beyond me.
[quote=nickdavies ]Fixed live shouldn't be going into the common on a 2 way switch. Look online for the wiring diagram for a 2 way switch should make it clear.
On the contrary - it's the only way to make it work properly. At least at one end. What you should have is wires between 1 of switch A and 1 of switch B; 2 of switch A and 2 of switch B; com of switch A permanent live; com of switch B goes to the light.
It depends how it was originally connected; a second switch added later may be connected differently to an installation that was originally two-way
There are 2 common ways of wiring 2 way lighting switches.
One has the incoming live going into the common at one end, then 2 wires(called strappers) to the nest switch, then the switched live outgoing from the common to the light fitting.
The other way is the incoming live to no.1 at one switch, then 3 wires going to the next switch, and the outgoing live from no. 2.
You need to 'bell out' the cables to find which are which.You'll need a multimeter to do it, once you have identified them, then there are loads of wiring diagrams online.
Or, you could keep swapping the cables round at the switch and hopefully get it right eventually.
Take a look at the diagrams on DIYNot.com. Once you 'get it' its easy, much better than guessing. When I did my house I had several 'two ways' and also managed a four way switch for a room that needed three light switches, lots of wiring but once you understand how it works, its not too bad.