Replacing 1 gang switch with 2 gang - now other rooms broke!

[shfanne]

I had a 1 gang switch that controlled 3 wall lights & a ceiling light in a bedroom.
I specified the design when barn converted so know there should be 2 circuits, I saw 1 wire out of wall for 3rd wall light & 2 wires for each of 1st & second & 1 wire from ceiling for centre light.
I switched off at mains which said all 3 beds & bath & as expected they all stopped working
Inside the switch box I have 4 cables, each has earth, blue & brown, all 4 blue wires were connected together, 2 browns went to top of switch & 2 to bottom, earths together & to switch.
I removed old 1 gang & got out 2 gang (which could be 2 way but I don't need that facility) and attached earths as they were to the switch.
The diag with new switch was for 2 way which wasn't helpful.
So I split browns & fastened 1 to top (L) and one to bottom (L1) of left gang & split blues to connect the matching pair together, so using all wires from 2 of the cables in. Left others unconnected & switched on - brill - wall lights went on and off as expected but ceiling stayed off.
So repeated pattern to L & L1 on right gang but no joy. Also tried each spare wire in turn wiring like 1 gang diag with brown at top (L) and blue at bottom (L1) - still no joy.
Now I find that whatever I do or don't do with the other 2 cables when I turn the power back on the lights in the other bedrooms don't work either!
Why would the power for other bedrooms be affected by the switch in this one???
(I did swap a switch some time ago in another room, 2 gang for 2 gang & there was a short wire connecting the 2 gangs directly so have tried this L to L too but makes no difference)
Anyone tell me what's going on?? Thanks.

 

[sparkwright]

at the old switch two wires in one terminal were feeds (feed in, feed out)

the two wires in the other terminal were live to wall lights and live to ceiling light

you need to re-identify these live brown wires

at the new 2 gang switch put a feed wire to common,
the other feed wire to the other common
and run a NEW SHORT PIECE OF WIRE between the two common terminals

then run wall light wire to one L1
run ceiling light wire to the other L1

don't use L2s

is this a dimmer, if so follow their instructions.

 

[sparkwright]

common may not be written on back of your new switch, there are variations. common is usually at one end on its own, with other two terminals at the other end. i take it from your description common is marked as just L.

typical 2-way terminal arrangements

com L1 L2

=

L1 L2 L3

=

L L1 L2

 

[shfanne]

No dimmer.
By COMMON do you mean the L on switch (I have 3 on each gang L at top, L1 and L2 at bottom)? Had been ignoring L2 as assumed for 2 way bit.
If 2 wires come out of the wall & jammed into same circle cut out together would they both be the ones from the light fittings, so other 2 be ones from mains? I have no tester just my trusty screwdriver.

 

[sparkwright]

yes i mean common is L
L1 is L1

and ignore L2s

 

[shfanne]

common may not be written on back of your new switch, there are variations. common is usually at one end on its own, with other two terminals at the other end. i take it from your description common is marked as just L.

typical 2-way terminal arrangements

com L1 L2

=

L1 L2 L3

=

L L1 L2

WOW thats service - you had answered my question before I had finished typing it!
Long pause now, miners helmet on, back for another go....

 

[shfanne]

This is interesting - 2 cables on left I guessed as to fittings & 2 on right to mains. So both "fittings" brown wires to both L1s and both "Mains" brown wires to Ls and the short bit across the 2 Ls. All 4 blues are connected together at present - should I have split these too?
Now the left gang turns on wall & ceiling lights in this bedroom and the right gang turns on the lights in the bedroom at the other end of the house! Should this be possible?????
(PS the house was wired from new in 2007 by qualified electrical company not me!)

 

[sparkwright]

you may have mixed up the browns.

the blue neutrals should remain together in one separate connector block.

 

[sparkwright]

This is interesting - 2 cables on left I guessed as to fittings & 2 on right to mains. So both "fittings" brown wires to both L1s and both "Mains" brown wires to Ls and the short bit across the 2 Ls. All 4 blues are connected together at present - should I have split these too?
Now the left gang turns on wall & ceiling lights in this bedroom and the right gang turns on the lights in the bedroom at the other end of the house! Should this be possible?????
(PS the house was wired from new in 2007 by qualified electrical company not me!)

possibly you have mixed the two feed wires with the two fittings wires.

 

[shfanne]

I have borrowed a tester and now know that 1 wire only is live, the other 3 are not. So that means the L to L must be live to other bedroom - ....... upstairs again ........... EUREKA. It is so simple & logical when you know what you are dealing with isn't it!!! The first assumption being wrong & it makes it all so confusing.
Thank you so much for hanging in there with me.

 

[sparkwright]

yes only one wire will be live. that is the live feed in.

this is THEN directly connected to another wire which feeds the other rooms. sometimes known as feed out.

the other two wires go to the light fittings.

if you can find the wire that goes to the other rooms and connect to that live wire, then you have found the two feed cables.

the feed wires go to the L terminals, with a link between.

you know the rest...

make sure you work safely.

 

[shfanne]

EUREKA. It is so simple & logical when you know what you are dealing with isn't it!!! The first assumption being wrong & it makes it all so confusing.
Thank you so much for hanging in there with me.