2 way switch wiring

[doctrain]

My two way switch which has run fine for 10 years is fed by a live from a two core cable. there is another two core cable going from that switch to the switch down stairs which is a double. the other downstairs toggle activate the hall light independently. I know everyone says It should be three core and earth - but it isn't and it has worked fine until my son tried to help by putting new covers on and forgot to make a note of the wiring.

The switch upstairs has a common plus L1 and L2 so does the one down stairs. The switch downstairs has a piece of wire going from one common to the other, and I believe the live feed upstairs (red) went into the common while the black wasn't even connected, it was in one of those lego type blocks. Sorry if it rambles but can anyone help get my lights working again

 

[mo2]

I didn't quite understand that posts, but it is most likely that the L1 and L2 are connected to the wire between the two switches so that the L1 upstairs is connected to the L1 downstairs and the same for the L2

 

[Adam_151]

Sounds like the T&E between the switches is being used as two 'strapers' and joins L1 on one switch to L1 on the other switch and the same with the L2 s, one of the switches picks a live feed upto com from another switch in the same bank, and the other switch has switched live leaving from com via a T&E with only the red connected and the black capped off

 

[breezer]

I know everyone says It should be three core and earth - but it isn't and it has worked fine until my son tried to help by putting new covers on and forgot to make a note of the wiring.

yes ideally it should be 3 core and earth, but if none available at the time you can use another twin and earth, as they have in your case, which is why the black is in a choc bloc, its not required