Lightswitch confusion

[JC]

Hi all,

I've replaced lightswitches etc before, but this one's got me stumped.

At M.I.L's house is a bedroom with two ceiling lamps. The existing switch is a double, I suppose to operate them independently. In actual fact the lights stay permanently on, whatever position the switches are in.

The existing switch is (I think) a double 2-way (two rows of L1, L2 and Common terminals). There are three wires in the mounting box -- red, blue and yellow, like one end of a 2-way system. There's no other light switch in the room*. It was connected with the red wire stripped in two places and screwed into both "common" terminals.

Can anyone suggest how to make this work properly? I don't care about operating the lights independently.

Many thanks in advance,

JC

*Probably. There are some built-in wardrobes, and I wouldn't be totally surprised if they cover up a light switch.

[dcbwhaley]

Do you mean the lamps cannot be switched off? Did this occur recently or have the lights been on since she moved in?

It sounds as if the red core is a live feed and the blue and yellow are the switched lives, one for each lamp. I would expect to find a junction box in the loft with an incoming supply cable, cables to each lamp, and the other end of the three core from the switch. For the lamps to be on all ther time either the switches are faulty or there is a short circuit in the junction box.

With the circuit isolated remove the blue and yellow wires from the terminals in the switch and insulate them. Restore the power. If the lights are now off replace the switch. If they are on call an electrician.

Dave

[Roger Mills]

Are you saying that if you remove the switches completely, and just have 3 un-connected bare wires, the lights are *still* on? If so, they are being switched somewhere else - and you need to find *where* - and modify that in order to bring this switch into circuit.

If the lights are *not* on when the wires are disconnected, you need to find what needs to be connected to what to bring them on, and then connect the switch(es) accordingly.

[JC]

Thanks for the reply. She's been in the house for years, and there were no bulbs in the lamps, so I don't know when it went wrong (or if it ever worked properly).

I'll try your suggestion. When you say "replace the switch", can I assume that the existing switch was of the correct type, i.e. 2 gang, 2 way?

And do I connect it up as it was before, with the red live in both "Common" terminals, yellow in the L1 of the top row and blue in L2 of the bottom row of terminals?

Part of my confusion was not knowing whether the correct switch had been installed, or if it had been installed correctly.

Cheers, JC

[JC]

No, they're not on when the switch is disconnected, thankfully! I wanted to try replacing the switch before more serious investigations, but wasn't sure if the existing switch was correctly wired.

Cheers, JC

[Roger Mills]

In that case, your previous assertion that they are permanently on - whatever positions the switches are in - surely can't be true?

[JC]

Yep, they were. There aren't many combinations to try with two switches, and I distinctly remember having to remove two hot bulbs :-)

JC

[Sparks]

In that case, there must be a problem with the switch or the way it is wired.

It is either part of a 2 way circuit or there was originally 2 separate circuits controlling each light. but someone has joined them together somewhere. I would guess from the symptoms, it was independent control at some point, unless the other switch (if fitted!) is also wired totally wrongly!

If at the moment, neither switch turns the light off, but the light is off when the switch is disconnected you must have the following connections..

The switch will look something like this

\ C\L1 L2 \ L1 L2\C \

All your wires are in either the top or bottom row (Except the red, this connects to both)

You need to wire it so both blue and yellow are in separate L1's or L2's, for example..

Red to the top C, then on to the bottom C Blue to the top L1 Yellow to the bottom L1

This will then mean either switch will be able to turn the light on, but the both need to be off for the light to be off.

It would be better to simply replace the light switch with a single switch, isolate one of the blue/yellow wires(chock block) then connect the red to C and the remaining blue/yellow to L1 or L2

[dcbwhaley]

Wire the new switch with red live in both "common terminals". Yellow in L1 of the first switch. Blue in L1 of the second switch. Ignore the L2 terminals, they are only needed for two way switching.

[dcbwhaley]

Is it possible that you have the blue and yellow going to l1 and L2 on the same switch. That would mean one or other, but not both lamps were on. If you had been trying all 4 combinations both bulbs would have got warm

[JC]

Ahh... I think you (and dcbwhaley) have got to the root of the problem. It was originally wired with red across the common as you describe, but with yellow to the top L1 and blue to the bottom L2. I'll try it the way you describe (ignoring L2).

Cheers, JC

[Dave Plowman (News)]

I'd start by disconnecting the switches totally, then switching the power back on. If the lights come on you'll know the fault is elsewhere. Often happens when people replace ceiling rose loop in loop out types with another lamp without this facility - they simply can't work out how to wire it. Of course normally what happens is they couple all the reds together and all the blacks. So the light is on with the switch off and the fuse blows with it on. In your case you have a yellow and blue to confuse them. ;-)

[Dave Plowman (News)]

A two way switch is a changeover type. If they've (as I suspect) used the blue and yellow as the switch returns for each individual light, then wiring them across L1&2 of *one* switch would cause one to be on with the switch in one position, and the other in the other. But there's no possible combination that can have both on at the same time and not switch off - unless the switch is faulty.

[Roger Mills]

That's right! I think the only way to have both lights on permanently, regardless of switch position, would be to connect all 3 wires to the *same* terminal.