two way switching with three core cable

[wps7581]

hi guys,

can anybody help me, i have moved a two way light switch from one side of the room to the other by a simple cable run from the existing switch point and to the new light i have wired it exactly the same but, only one switch at a time will work, i.e if the downstairs switch turns the light on the upstairs one will work fine? but if just go to use the upstairs switch it doesnt work any ideas please

 

[RF Lighting]

Hi how are the switches currently connected? i.e. which cores from which cables go to which terminals on the switch? Can you take photos so we can advise where you have gone wrong

Rob

 

[wps7581]

hi rob,

thanks for getting back to me, basically wear the switch used to be i have extended the cables i have a single permanent live which is the neutral and obvioulsy the link between the two, upstairs in the common is a single red wire in L1 is the other live red wire in L2 is the black neutral wire, downstairs in the common is the single black neutral wire, in L1 is the red wire in L2 is the neutral black wire, i hope this helps

 

[RF Lighting]

Hi not sure as of yet what the problem is.
The wires which you are refering to as 'neutral' wires - are these definitely neutral wires or merely black coloured wires? It is more likely that these are black coloured switch wires (which should have had a piece of red sleeving fitted to them to avoid exactly this sort of confusion)

Are the wires singles (1 red or black wire within a grey outer sheath(may also have an earth wire too))
Or are they twin and earth cables (a red and black wire within a grey outer sheath (this will contain an earth wire))
or a combination of both?
If so note down which core from which cable is connected to each terminal.

Hope this makes sense and will try to help further.

Any chance of some quick snaps of the offending switches as this will really help thanks

 

[MANDATE]

Firstly you have to understand there are two different methods of wiring a set of two way switches.
Basically the modern method uses a 2 core cable (red and black) to one of the switches and a 3 core cable ( red ,yellow and blue) to link between the two switches. This means 5 wires at one switch and 3 wires at the other.
The old method used 1 wire (red,live) to switch no 1 then a 2 core cable between the two switches and then another single wire from this switch to the light. This means 3 wires at each switch.
So you need to confirm which method you have. Now because you have not mentioned blue or yellow wires I'm thinking you have the old method.
For this the red 'live' comes to SW1 into term. 'com'. At the second switch a wire leave term. 'com' it could be red or maybe black but it should have red flag to indicate it may be live. This wire will go to the light. Now the terminals L1 and L2 on both switches are linked across.
Wires before the 'light' are either 'live' or 'switched live' regardless of the colour. It is only after the light it becomes 'neutral'
You should be able to indentify the incoming 'live' at one of the switches.
Then at the other switch with three disconnected wires one will be live and another will become live when you flick the switch leaving one wire dead. This dead wire should be placed into 'com' and the other two in L1 and L2 ( no particualr way round).