3 way double switches for 1 bulb?

[micromart123]

Hi,

In my living room I have a double light switch that controls the living room light. On the other side of the living room door I also have a double light switch that controls the light in the living room. They are both double switches and yet they only turn on one light.

So I've bought 2 two-way single switches to replace them, but I have no idea how to wire them up because it looks like they've been wired in a 3 way set up?

Any ideas would be good, I've attached the wiring of the switches as they were before I took them off the wall.

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• micromart123
• 2 Jul 2013
• 1

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• micromart123
• 2 Jul 2013
• 1

 

[EFLImpudence]

At first glance the wiring does not seem to make sense.
Have you moved any of the wires?

In the left hand picture, does the 'top' switch control anything?

 

[stem]

The bottom photo is just controlling one light, so it will simply be a matter of exchanging the wires like for like.

The photo you have posted appears to show

L1 (black / red sleeve)
L2 (Yellow)
L3 (Blue)

Other switches have Com (common) L1 & L2

If so this would be:

Com (black / red sleeve)
L1 (Yellow)
L2 (Blue)

With the other switch it has wires for another light. I assume that it doesn't work otherwise replacing a two gang switch with a single gang one will cause you a problem.

Any unused wires will need to be disconnected / isolated and made safe.

 

[micromart123]

In the left hand picture the top switch doesn't turn anything on. The bottom switch turns the light on.

I think the light switch in the left pic is the original light switch and the switch on the right pic has been added afterwards. But I'm not sure how they've managed to wire it up.

 

[micromart123]

Hi stem,

I've just seen your reply, I will turn the power off and change the light switches around and see how I get on.

Thanks,

 

[micromart123]

Working now! I'm thinking the red and black cables are for an exterior light that is not connected up - the cables are dangling above the exterior door taped up!

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• micromart123
• 2 Jul 2013
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• micromart123
• 2 Jul 2013
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[EFLImpudence]

You must connect the CPCs (earths) to the metal switch.

with an extra wire sleeved green and yellow to the back-box if the cable CPCs are too short.

 

[stem]

I'm thinking the red and black cables are for an exterior light that is not connected up

Not an exact science then There could still be a live supply connected to the switch wires from elsewhere, depending upon how it was wired in the first place. It would be good if you don't plan to use it, to have the circuit disconnected properly. As a minimum the wires at the switch should be insulated in separate screw connectors. EFLImpudence is correct, the metal faceplate also needs to be connected to earth

 

[ban-all-sheds]

So I've bought 2 two-way single switches to replace them, but I have no idea how to wire them up because it looks like they've been wired in a 3 way set up?

How can 2 switches be a 3-way setup?

So you've gone from this:

to this:

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• micromart123
• 2 Jul 2013
• 1

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• micromart123
• 2 Jul 2013
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and everything works OK?

 

[ban-all-sheds]

You must connect the CPCs (earths) to the metal switch.

with an extra wire sleeved green and yellow to the back-box if the cable CPCs are too short.

The ones in the 3-core & earth appear to be very short.

micromart - the sort of idiot who would do that could have visited his idiocy on any other part of your electrical installation. Just connecting the cpcs in the cables and assuming that they work would be very foolish - you must check that there is continuity back to the CU.

 

[micromart123]

Okay, this was the initial set-up with a plastic front on it:

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• micromart123
• 2 Jul 2013
• 1

And that was a double switch for an outside light (not connected up) and the living room light. Now it looks like this:

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• micromart123
• 2 Jul 2013
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So am I correct that what I need to do now is earth the light switch with the green and yellow earth connected to the back of the light switch and tape off the unused black and red wires?

Now the other old plastic switch that looked like this:

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• micromart123
• 2 Jul 2013
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Now looks like this is:

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• micromart123
• 2 Jul 2013
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That earth wire is too short to reach the back of the switch so do I need to add more earth wire so it reaches to the back of the switch?

I've got a continuity tester screwdriver how do I check continuity back to the CU?

 

[EFLImpudence]

So am I correct that what I need to do now is earth the light switch with the green and yellow earth connected to the back of the light switch

Yes, to both of them.

and tape off the unused black and red wires?

Put each of them in a separate connector block.

Now the other old plastic switch that looked like this:

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• micromart123
• 2 Jul 2013
• 1

Now looks like this is:

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• micromart123
• 2 Jul 2013
• 1

That earth wire is too short to reach the back of the switch so do I need to add more earth wire so it reaches to the back of the switch?

Yes.

I've got a continuity tester screwdriver how do I check continuity back to the CU?

You will need a long wire.
Test continuity between the CPCs (earth wires) and a nearby socket screw, obviously one with a metal back-box, or something else which is earthed, water pipe, appliance carcass, metal hob, oven etc.

 

[securespark]

Best way is to scrap your screwdriver (or at least only use it as such) and buy a multimeter (starting from a tenner at Maplin).

When you have stripped back the cpc, put a terminal block on it then put the power back on and use the DMM to measure the voltage between live and the CPC: you should get 216-252V if you have proper continuity.

If not, you could get any reading, from a few volts upwards...

Or, you could do it without power, checking continuity from an adjacent outlet, using the continuity setting on the MM.

Edited for clarity.

 

[ban-all-sheds]

And that was a double switch for an outside light (not connected up) and the living room light. Now it looks like this:

So the 3 R/Y/B cores are now connected differently to how they were before.

So am I correct that what I need to do now is earth the light switch with the green and yellow earth connected to the back of the light switch and tape off the unused black and red wires?

Yes, you need to earth the switch, having proved that the cpc is connected to earth.

Use choc-block on the end of the unused cable, not tape.

That earth wire is too short to reach the back of the switch so do I need to add more earth wire so it reaches to the back of the switch?

Is it a metal switch?

I've got a continuity tester screwdriver how do I check continuity back to the CU?

Do you mean a 2-pole continuity tester screwdriver, or a neon screwdriver?

 

[micromart123]

So the 3 R/Y/B cores are now connected differently to how they were before.

Yes, the 3 R/Y/B are on one switch now whereas before the yellow wire was on a switch with the black wire (For the outside light) and on the other switch it had the red wire and the red wire (For the outside light) and the blue wire connected to it, as you can see if you follow the wires back:

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• micromart123
• 2 Jul 2013
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That's what confused me because the wires were spread across both switches even though only one switch controlled the light.

I will use blocks instead of tape on the red and black wires that are not connected.

The earth does reach the back of the switch so I've connected it to the back of the metal switch now.

The screwdriver I've got is this:

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• micromart123
• 2 Jul 2013
• 1