After attempting to change light switch, lights no longer work

[lefty83]

HI
I tried to change a light switch and now the lights in the room where the switch is located as well as the passageway no longer work.
I only saw 2 wires connecting the old light switch, both were the same colour, but I didn't make a note which way round they connected.
Connected the wires in L2 and COM in the new switch, powered the mains on and lights didn't work, opened up and realised the wire needed to go in L1 so did that, again didn't work, so switched off mains and swapped the wires around, thinking maybe I had wrongly connected the COM and L1 wires.
Still doesn't work, connected the old switch back and nothing and tried the wires both way round, but cant get the lights to work.
Left the wires unconnected to see if I got power to the passageway but no power to that even when the non working room light wasn't connected.
Any ideas how i get this fixed, or have I blown something?

 

[Jackrae]

Did you remember to switch the power off before you started and have you remembered to switch it back on afterwards.
Do other house lights, apart from the ones you mention, still work.
It matters not which way round the wires go (if there re only 2) but one of them must go into the COM connection. L1 versus L2 defines whether switch is UP or Down for ON
Photo essential of wiring and the box that the switch is mounted in - are you sure there are only 2 wires

 

[lefty83]

HI
Yes I switched off the entire house power, and did so every time I attempted to try and fix the issue.
Yes switched on every time I tried and this room is the only room where the lights do not work (including the passageway) all other rooms including the dining room work fine (I changed the dining room one prior to doing this room and that is working fine, although i recall that had 3 wires, so placed 1 in each of the L1/L2 and COM)
Yes I checked a number of times to see if there was more than 2 wires, but 2 is all i could see

 

[Jackrae]

Did that switch normally operate both room and passageway lights ?
If not is the passageway light switch immediately adjacent to or at the immediate rear of this switch
A photo really would help

 

[lefty83]

Hi,

I'm not at home to take a pic, can do tonight hopefully, would you need the pic of the wiring of the switch?
Yes the switch worked fine before i attempted to change it, and no the switch i attempted to swap only operates the room, the passageway way switch and the stairs switch are different and both do not work since this issue, but did before.

 

[terryplumb]

You have done something wrong at the dining room switch ,and lost the supply to the others. Do you have any electrical testing equipment , like a multimeter or a two probe voltage tester ?
After changing the dining room switch ,did you check the old switch ( in the room that now doesn't work) was still working before removing it ?

 

[lefty83]

Hi,
Hmm i wouldn't have thought it would be the dining room causing the issue, as that's working.... but because I cannot figure out what is wrong with the living room I can definitely have a look at the dining room one again.
The old dining room switch had 3 wires but the old switch only had L1 and COM, i'm pretty sure I put 1 wire in L1, 1 in L2 and 1 in COM in the dining room switch and that works, so assumed there was no issue there, just to clarify, what are the possible issues that would cause the dining room to work, but mess up other rooms?

I dont think I tested the switch in the living room that no longer works, before I changed it, but had been working the day before.

 

[Jackrae]

The reason I asked about an adjacent switch, that controls the passageway light, is that you may have accidentally pulled out a live linking wire on that switch

Trouble shooting by questions really is "shooting in the dark" (pun intended)

"One wire in each terminal" on the dining room switch sounds suspicious. Did you note which wire went where BEFORE you removed the old switch. How many switches controlled the dining room lighting. If 2 independent ones then it's probably a 2-way circuit, but if only the 1 then you should have used only 2 terminals and 2 of the 3 wires were probably linked together. Welcome to the world of lighting wiring mysteries.

 

[terryplumb]

Hi,
Hmm i wouldn't have thought it would be the dining room causing the issue, as that's working.... but because I cannot figure out what is wrong with the living room I can definitely have a look at the dining room one again.
The old dining room switch had 3 wires but the old switch only had L1 and COM, i'm pretty sure I put 1 wire in L1, 1 in L2 and 1 in COM in the dining room switch and that works, so assumed there was no issue there, just to clarify, what are the possible issues that would cause the dining room to work, but mess up other rooms?

I dont think I tested the switch in the living room that no longer works, before I changed it, but had been working the day before.

Dining room has 3 conductors.
One is the permanent line
One is the switched line
What do you think the third one is ?
I suspect it's the supply line to the other switches that now do not work ,because you have not connected it to the permanent line.
Have you worked on any other switches or light fittings that you haven't mentioned ?

 

[lefty83]

HI both,
I've got a pic of how the dining room was before i made the change... i didnt take a pic of the living room as thought its only 2 and both are the same colour so taking a pic i didnt think would help.
But the dining room, only has 1 switch. See pic of the old set up of the dining room, which shows both the wires connected to the non COM port.... do you guys think i should change this on the new switch in the dining room and put both those into L1, currently i'm sure i put 1 in L1 and 1 in L2.
Other than these 2 light switches no i didnt work on any others, worked on sockets and tested each one as i changed them around.

 

[terryplumb]

Exactly as I thought. The two conductors that are in the same terminal in your pic ,should go together in the com terminal in your new switch. The third goes to L1.
By the way the old switch is wired incorrectly ,but would still have worked fine ,along with the others.

 

[lefty83]

Thanks, So the old set up in the dining room pic shows as 1 wire in COM and 2 in the other.
Should i wire the new switch like so the 2 wires which are visible in the pic which were in L1 move them both to COM... and the 1 visible in COM move that to L1?
I'm sure the way i did it in the dining room was, the one i removed from COM i put in COM, and the other 2 from L1 i put in L1 and L2.
WOW if this is the problem i would never had even thought about looking at a room which is working!

 

[terryplumb]

Com is the terminal that contains the permanent line( or lines if more than one). When you switch it on ,you connect com to L1 ( internally). When switched off ,com is connected to L2.
So the conductors in L1 and L2 never connect to each other.

 

[terryplumb]

Thanks, So the old set up in the dining room pic shows as 1 wire in COM and 2 in the other.
Should i wire the new switch like so the 2 wires which are visible in the pic which were in L1 move them both to COM... and the 1 visible in COM move that to L1?

Yes

 

[lefty83]

Thanks will give it a try this eve and report back tomorrow