light switch wiring

[selbyreb]

I have a two gang switch in my hallway which operates the hall lights and also a light outside the front door. The switch for the hall lights is two way with the corresponding switch to operate the hall lights situated in the kitchen. There is no problem with this part of the two gang switch, however I want to operate the outside light independently of the hall lights but at the moment the hall light must be switched on before the outside light will work. The part of the two gang switch will turn the outside light on and off but only when the hall light is on. On checking inside the two gang switch the following cables exist. One 1.5mm twin and earth, two separate earth wires and three single cables (1.5mm). The switch is wired as follows. The twin and earth has the red core going to L1 on the two way switch and the black core going to L2. One of the singles goes to the common on this switch. The switch which operates the outside light has one single going to the common and one going to L2. There is also a connection between the two common terminals. All three earth cables are connected to the metal back box.
Any help would be much appreciated

 

[ColJack]

you can't do it..

you have no permanent live at that switch.. you only have the 2 strappers and the switched live back to the light...

the 1 way switch wire is missing a live.. you might want to check in the ceiling rose of the hall light, or there may be a seperate junction box somewhere which connects the outside light...

you need to find the single that is connected in the common terminal at the switch.. do you have a multimeter? they're cheap enough from any of the DIY sheds..

when you find it, connect it to the permanent live ( I'll assume you know to turn the power off before messing in the switches??? ), and then DISCONNECT the link in the switch between the commons.. or your hall light will not go off...

 

[sparkieno1]

Just to add that the permanent live could also be in your outside light you would also need some sort of voltage tester to check this.If you do find a permanent live it should be connected to the red of the cable going to common of light switch and the link removed,the returning black wire(switched live)coming from L2 should be connected to live on your o/s light the neutral being the black wire in the same cable as your permanent live, earths should be joined and screwed onto earth terminal.There is another way of wiring 2 way switches(more modern method) which gives you a permanent live at both switches and old wiring can sometimes be changed to do this but only in certain circumstances and would be difficult to explain on here.

 

[ColJack]

not other T+E present.. the only T+E at the switch is the strappers.. the other wires are run in singles..

 

[securespark]

Col

Am I missing something? How do you know the common for the two way isn't the live feed, not the switchwire?

 

[sparkieno1]

You have to open up your O/S light,if there are only 2 cores(+earth)and they go to common and L1 or 2 in your lightswitch you do not have a neutral and it is wired wrong.check your O/S light + let us know.

 

[selbyreb]

Thanks for the info fellas. I have a multimeter so can check at the outside light. Not sure if the hall light is connected via JB or ceiling rose but I'll check

 

[selbyreb]

One other thing which I found out is that the red and black cores of the T&E which operates the hall light read 230 volts with the meter across them but when the switch is operated the voltage is reduced to 185. Does this sound correct?

 

[ColJack]

Col

Am I missing something? How do you know the common for the two way isn't the live feed, not the switchwire?

good point, didn't cross my mind after reading the OP's post I just assumed it wasn't since the outside light only comes on when the hall light is on, indicating to me that it's not live untill the light is on, and also that there is a third single from the switch which is not needed if it already has a live feed at the switch.. ( why run an extra single to bring in what another single is already taking there? )

I guess it was just a logical assumption..

One other thing which I found out is that the red and black cores of the T&E which operates the hall light read 230 volts with the meter across them but when the switch is operated the voltage is reduced to 185. Does this sound correct?

yes this is fine.. with the switch open you are reading the 230V on the open wire ( live the other end ) and through the switch and the lamp to neutral on the other wire..
when the light is on, you are reading 230V on the closed wire through to... nothing on the other wire ( open both ends ) and is therefore floating a little above earth..