light only works if other is on

[munia]

HI - I recently changed a 2 gang 2 way dimmer swicth to a normal 2 gang 2 way switch as I thought it was causing this issue...but it didn't

I have 2 ceiling lights either side of the lounge, I can turn one light on and off independantly but the other light requires the first light to be on. I have 2 red wires that go into L1 & L2 and 1 black wire into COM 1 then a small bit of black wire from COM 1 to COM 2 - earth connected to term box - The new swicth has marking for L1 & L2 for 1 way or 2 way...not sure if that makes any difference. Any help would be much appreciated.

Thanks
M

 

[Adam_151]

Your description is hard going!

If its a two gang switch, you should have two lots of COM, L1, and L2, you have described two coms, but only one L1, and only one L2, please tell us what you have per switch... or better still draw us a diagram

Are any of these lights switched from other locations?

How are these conductors grouped into sheaths?

 

[ColJack]

generally, the black is the switched live, so the mains is coming in on one of the red wires..

since there are 2 red wires and 1 black wire it's probably a safe bet that one of the red wires is part of a twin and earth with the black.. it will be this red that is the live..

take the black out of common and swap it with the live red.. leave the 2 commons linked together..

EDIT: wait.. I didn't read your description properly it seems..

as said above your description is a little confusing..

we need photo's of the back of the switch please..

 

[munia]

I'll try and get a photo, but in the mean time - the RED/BLACK & EARTH are part of the same single cable from the wall, the 2nd red seems to come from an existing light switch controling some ceiling mounted spots along a back wall also in the lounge.
Thanks for your quick replies.

 

[munia]

I have drawn a picture that I hope will make things a bit clearer...

http://tinypic.com/view.php?pic=2cdwl8k&s=3

As I mentioned the red going in to L1 is on it's own (without a black or earth wire) and could be from a switch on the other side of the wall. The other red is part of the same cable with a blck and earth wire.

The switch does indeed have 2 L1's and 2 L2's and 2 COM's

 

[ColJack]

then my original sugestion was almost right.. swap the single red for the black...

which switch has to be on for the other to work?

 

[munia]

Thanks for the reply and patience ColJack - is this what you mean...

http://tinypic.com/view.php?pic=4g2e4i&s=3

The L1 switch needs to be on before L2 lights will switch on

Thanks again

 

[ColJack]

er, no not quite..

leave the 2 commons linked but swap the red single for the black in the twin..

 

[munia]

Thanks ColJack, I'll give it a go and let you know how I get.

Thanks for all you help with this, very much appreciated.

 

[munia]

IT WORKED! - Many thanks ColJack, the lights now switch on and off independently. Thanks for all your help with this.