2-way 2-gang, 2-way 1-gang problem

[shaneybaby55]

Hi I have spent a few days looking around forums and am struggling to find an answer, for the little problem that my partners parents have, hope somebody could help us out, would be much appreciated. A wall lamp was replaced the other day at the bottom of the stairs this lamp works off a 2-way 2-gang switch, which also works the light at the top of the landing. At the top of the landing there is a 2-way 1-gang switch. I do not know if the problem persisted before, but if you turn the light off using the upstairs switch and tried to turn it on using the downstairs switch it does not work.

I looked at the lamp that was wired and you have brown cable connected to brown cable, blue cable connected to blue cable, and of course the earths were connected.

I have not touched the downstairs wiring on the 2-way 2-gang switch, here is a photo of it
http://img.photobucket.com/albums/v150/swillson/IMGA3707.jpg

As you can see top row, com red wire, L1 red wire and L2 black wire
Bottom row, L1 red wire which also has a red wire to the com and L2 is empty. These wires come in from 3 main white cables, there is also 2 black wires that are connected as you can see.

When I opened the 2-way 1-gang switch at the top of the landing, there was a red wire, which was not connected, it looked if the end had snapped and was just hanging there. Along with this red wire, there is 1 more red wire along with 2 black wires; these wires come in from 2 main white cables.

I have also noticed that the earths are not connected to the metal mounting boxes at either switch, the switches are plastic, is this why they have been left disconnected?

All advice welcome

 

[stem]

You don't say where the wires are connected at the switch upstairs. For example:

cable 1 red - Not connected
cable 1 black - Common terminal

cable 2 red - L1 terminal
cable 2 black - L2 terminal

This may help understanding how the system is wired and where the red wire should go, if anywhere

If the back boxes are metal they should be earthed. It could be that someone has had metal switches on at some time and just disconnected the wires when they replaced them with plastic.

Why don't you know if the problem persisted before? Didn't your partners parents ever use the light?

Does the landing light work OK? or does this problem just occur with the wall light?

 

[shaneybaby55]

Hi stem, thanks for reply, I did try a few routes,but can not get the landing light to work as it should, ie turn on and off using both switches, the wall light works fine no problems, it's just getting the landing light to work using both switches, I forgot to note down how the wires 3 that were attached were fitted. They do not recall having a problem before the wall light was fitted, but they are unsure.

I can get the landing light to come on and off using the downstairs switch, if you turn it on from downstairs then off from upstairs, it does not go on again by using the downstairs switch.
Does it make any difference that 3 main cables are coming it downsairs and only 2 upstairs?

 

[stem]

Does it make any difference that 3 main cables are coming it downsairs and only 2 upstairs?

No this is what I would expect. There are several methods of wiring 2-way switching. From your photo, it looks to me to be wired as follows:

The live will be supplied via the red link at the bottom of the downstairs switch in your photograph. This will, depending on the position of the switch be switched out to either the red or black wire connected directly above (probably from terminals marked L1 & L2). Those two wires will then be connected to terminals L1 & L2 in the switch upstairs.

The common (central) terminal at the switch upstairs will then be the switched live supplying the light(s)

The if the wall light works correctly, only the landing light doesn't, the switching is working OK. I would suggest the fault lies elsewhere. The disconnected red wire could just be a spare core that is not used or it could be needed, try and find the other end in the loft and see if it's connected to something.

 

[shaneybaby55]

Here is a photo of how it was wired, as this is the only way it works with the red out (when I say works I mean I can get the landing light to come on and off using the downstairs switch, but if you turn it on from downstairs then off from upstairs, it does not go on again by using the downstairs switch.)
http://img.photobucket.com/albums/v150/swillson/IMGA3709.jpg
I can not find where the red goes but everything else is working.

I am right or wrong in saying that whatever wire is in the common terminal downstairs, that wire must go in the common terminal upstairs? So as there are 2 red wires in the common terminal downstairs, should a red wire be in the common terminal upstairs?
Also is it a no no to have a black and a red wire going into the same terminal?

 

[stem]

I did try a few routes,but can not get the landing light to work as it should,

So the landing light does not work properly.

The wall light works fine no problems, it's just getting the landing light to work using both switches,

So the wall light does work properly.

From what you say above, my understanding is that both lights are connected to the same switch. One works correctly and one doesn't. Please confirm this as your last post confused me a little bit.

is it a no no to have a black and a red wire going into the same terminal?

Yes, but it used to be done like this. Ideally the black wire should have a red sleeve on it.

Am right or wrong in saying that whatever wire is in the common terminal downstairs, that wire must go in the common terminal upstairs?

No. You're wrong. The live to the lights is from the common terminal upstairs.

The live supply (from the consumer unit) goes to the common terminal downstairs

L1 & L2 downstairs are connected to L1 & L2 upstairs

(There is an alternative way of wiring where the commons are connected, but this is usually used where an existing one way switch is converted to a two way. Doesn't apply in your case)

The connections look correct to me, although I would have expected the red wire to be used as the supply to the lights from the common of the upstairs switch rather than the black. Pity you can't find where the red goes.

 

[shaneybaby55]

Thanks for your time and replies stem.
The wall light downstairs works fine, the landing light upstairs is the one I am having trouble with. There is a single switch upstairs that works the landing light and there is a double switch downstairs that works the wall light and the landing light.
so quite possibly, it maybe then that a red and black were connected together as I think this way of wiring looks pretty dated to me and I am not an expert.
I'll have another look to see where that red goes

 

[stem]

OK great, sorry my misunderstanding. We'll ignore the wall light downstairs now as it's not connected to the two way switching at all.

Here's a link to a diagram that shows what you have. Yours is diagram 1. The neutrals are omitted for clarity.

http://en.wikipedia.org/wiki/Switch#Two_locations

"From the mains" is the downstairs switch, "to light" is the upstairs switch.

A & D are the common terminals, B & C are L1 & L2

Putting everything together I think the wiring is probably OK, you may simply have a a faulty switch.

If you have a multimeter, check with the downstairs switch that you have mains on L1 or L2 this should swop from one to the other as you operate the switch. If one is missing the switch is faulty.

If that's OK, the easiest way to check the upstairs switch is to buy (or borrow from somewhere else) a replacement and try it.

 

[ColJack]

i recon you either have the wrong red in the terminal at the bottom, meaning that you age only switchingblack to black. and that the red is the spare..

or.....

you have the 2 blacks the wrong way round..

meaning you have the switch feed to the light in L2 ( or L1, can't tell from the pic.. ) and the strapper to the COM..