Adding an outside light

[Andy Monk]

I have a (hopefully) simple question. In my lounge, I have a single light, controlled by two light switches (each switch at opposite ends of the room). Now, I want to add an outside light, and for it to be using the same power as the lighting in the lounge, as one of the lounge switches is on the wall next to the back door - I thought I could use this switch (somehow) and just control the outside light (it's never used otherwise). I figured that I couldn't just do that, as it's linked to the lounge light.

So, I bought a 2 gang switch, which in my mind will have one switch to retain the existing lounge lighting, and the other switch to control the outside light.

My question is, how do I wire this? There's only one permanent live, which needs to go to 2 common inputs, so I joined the two common inputs, but now the second gang switch is always on... picture attached, and any help is appreciated!

 

[endecotp]

I'm assuming that in your picture, the white flex is for the new outside light [why flex??] and the black/brown/grey is the existing cable for the inside light.

If that's true, you can't do what you want because you don't have a neutral. (It's also possible that you don't have a permanent live; the brown wire will be permanent live at one or other of the two switches for this light, but not both - if it's wired in thr most conventional way.) So you will need to make a connection somewhere else, perhaps at a light fitting or junction box above the ceiling.

 

[Andy Monk]

Thanks for your reply.

Not sure about the flex question... It's just what I had. What should I be using?

Yes, the black/brown/grey are for the existing light switch. The black wire appears to be always on; so is that not permanent live?

Unfortunately, I don't have any connections closer, and my walls are solid - which makes it a messier job to chase cables in the wall etc...

 

[ban-all-sheds]

If that's true, you can't do what you want because you don't have a neutral. (It's also possible that you don't have a permanent live; the brown wire will be permanent live at one or other of the two switches for this light, but not both - if it's wired in thr most conventional way.)

Well, it depends of course by what you mean by the "most conventional way", but I would say that was this:

in which case of course there will be a permanent live at each switch.

However...

1) Subject to confirmation, I think the OP may have this:

2) You're right about the neutral.

 

[Andy Monk]

That makes sense... I believe it's the second diagram, as that appears to resemble the logic. Oh well, I'd better find an alternative power source...

Thanks guys

 

[ban-all-sheds]

Yes, the black/brown/grey are for the existing light switch.

You should have an earth connection to the new one.

The black wire appears to be always on

As shown by what? Neon screwdrivers and magic wands are not to be relied on.

Unfortunately, I don't have any connections closer, and my walls are solid - which makes it a messier job to chase cables in the wall etc...

There is no neutral at that switch - you simply will not be able to power a light from it.

 

[Andy Monk]

Thanks again. I'm obviously not an expert, so as far as I knew neon screwdrivers illuminating means current is flowing. Perhaps I should've touched it to make sure?

 

[ban-all-sheds]

They allegedly indicate the presence of a voltage, not current flowing - the two are not the same: https://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law

But they are unreliable, and not necessarily safe to use. A two-pole voltage detector or multimeter should be used.

 

[Andy Monk]

Ok thank you, a valuable lesson learned!