Electrical switch problem (2 gang)

I realise this might be difficult to answer, but any ideas. This probably was originally wired like this since installation years ago, but as I never use the outside light it hasn’t been discovered.

In my lounge I have a 2 gang switch by my front door.

On the switch the right hand switch supposed to work the outside light. The left hand switch supposed to operate the lounge light.

However, today gone to put a new bulb in the outside light & it came on though the right hand switch was off.

When I put operate the left hand switch (lounge one) the lounge light comes on and the outside light goes off & when the outside light is on, the lounge light goes off. It's one or the other.

However the right hand switch (which supposed to be the outside light) does nothing.

It’s like the electrician has wired the outside light to the lounge light?

Is there any diagrams anyone can point me too.

If you feel safe and the wires are long enough,

isolate the supply, unscrew the switch, and take a photo of the wires going into the back of the switch.


If your lounge only has one switch point for its light (1 way) then you should only have a wire in terminal L1 OR L2 and not both.

I suspect each switch is a change over switch and the switched Lives from lounge lamp and outside lamp have been wired to the same switch instead of one to each switch.

Each switch will have three terminals. COM L1 and L2

The two COMs should be linked, one will have a wire in it, that wire stays where it is. there will be two other wires connected to the L1 and L2 of one switch. The one going to L2 should be moved to the other empty L1

Turn the power OFF at the consumer unit before starting work. Make notes about which wires go where in case this is not the simple solution and more changes have to be made.

Thanks for the replys. I'll pull apart the light switch again at the weekend.

Though from memory earlier. I think there a wire going from L1 on the left hand switch to the COM (top terminal on the righthand switch. If COM terminals are both at the top there certainly wasn't a loop between the top 2 terminals. The only join was from either L1 or L2 (bottom terminal to the top one on the other switch.

Maybe this would explain when turning off the lounge light; the outside light then gets a live feed on?

When you say the RH switch does nothing, have you tried operating it with the LH switch in both positions?

I suspect that when the LH switch allows power through to the RH switch, you might find operating that switch will turn the outside light on and off as it should.

If it does not, then you have both wires for that switch in the same terminal.

If indeed there is a link from L1 on the lounge switch to common on the outside switch, this needs changing so that the commons are linked to each other but not to any other terminal.

It seems that the wire connected to the common of the lounge switch is a live feed so that can stay.

Then the other wires (1 switchwire each to the lounge and outside lights) need connecting to L1.

Things will be a bit different if your lounge light is 2 way.

many thanks for the replies.

This switch sorted now, all working ok. The lights now work spearately.

However the lounge switch is 2 way & having a problem with the oher switch. I have made a separate post on this as the other swtich doesn;t control the lounge light.