Light switch issues need help

[saturdays]

Good morning,
I was decorating yesterday and decided to remove switch cover to don't get it dirty. Unfortunately one of wires came loose or was loose already, because when I was unscrewing there it was sparking. Could someone please tell me where missing wire is from because I can't find it in any diagrams in Google. Thanks Robert

 

[westward10]

It is either L1 or L2 try it in each one it won't do any harm.

 

[littlespark]

It is either L1 or L2 try it in each one it won't do any harm.

This….

But isolate the circuit first.

 

[brianmoooore]

because when I was unscrewing there it was sparking.

Good idea to isolate the circuit when doing this as well!! You wouldn't be the first to have a loose live wire spring out from its home and make a bee line either for your finger (which will hurt), or for the earthed metalwork (which will frighten the life out of you).

Looks like a 25mm deep metal box in a hole that would take a 47mm one. Why??

 

[brianmoooore]

It is either L1 or L2 try it in each one it won't do any harm

Either L1 or L2 will be a permanent live, so the disconnected wire is either live in or live going on to another light circuit.
When you've connected it, check that other lights in the house still work with this switch in either position.

 

[littlespark]

Educated guess. L2

The cable that has come out is the grey from a 3 core. The coresponding black from same cable is in Common, the brown is in L1

 

[brianmoooore]

Educated guess. L2

The cable that has come out is the grey from a 3 core. The coresponding black from same cable is in Common, the brown is in L1

I thought the disconnected cable was a sheathed black single.

 

[westward10]

It's grey.

 

[littlespark]

Looks to me grey, coming from bottom right hand hole in box…. Half in shadow might make it appear black.. and it’s got brown sleeving at end.

 

[brianmoooore]

It looks exactly like a sheathed single on my PC, but I've just pulled the same pic up on my phone, and yes, the black part does look like shadow there. Definitely grey at the end as well, so I'll concede - it's a grey out of a 3 core + E.