How to change a double light switch to a dimmer switch

[shazza]

Just moved into an old house, and trying to replace a double light switch to a double dimmer light switch.

The current switch operates the wall lights in the through lounge, so we have one room with 3 wall lights and the other room with the same, no ceiling lights.

The wiring is as follows; two red wires and one black wire, there is also a red crossover wire linking both L2s together.

L2 = black wire, L2 = red wire and L1 has a a red wire which crossover to the other L1.

We thought maybe a dimmer switch was not possible, so purchased a replacement double switch. However, when we rewired this exactly the same, nothing worked at all.

Thanks.

 

[ban-all-sheds]

However, when we rewired this exactly the same, nothing worked at all.

One of these is true:

1) A brand new switch is faulty.

2) You broke a cable.

3) You messed up one or more connections and the conductor is not in contact with the terminal.

4) You did not rewire it exactly the same.

Look in the For Reference section for diagrams of how light switches are wired - don't stop after the first one, as it's a bit of a mish-mash right now, and there are different diagrams of differing quality and clarity....

 

[shazza]

However, when we rewired this exactly the same, nothing worked at all.

One of these is true:

1) A brand new switch is faulty.

2) You broke a cable.

3) You messed up one or more connections and the conductor is not in contact with the terminal.

4) You did not rewire it exactly the same.

Look in the For Reference section for diagrams of how light switches are wired - don't stop after the first one, as it's a bit of a mish-mash right now, and there are different diagrams of differing quality and clarity....

100% sure it was rewired the same and everything was double checked. So it cant be any of the above 4.

Are old double light switches any different to the new style? also be copying the current setup of the double dimmer switch, why would this not work?

We have managed to get it working so that we can have one set on in each room, but not get both on together.

 

[ban-all-sheds]

100% sure it was rewired the same and everything was double checked. So it cant be any of the above 4.

Well maybe somebody else can think of a (5) then...

Are old double light switches any different to the new style?

Quite possibly, as new ones are different from new ones too.

Some have L1/L2/L3, come have COM/L1/L2.

Some have the terminals grouped in triangles, some do not.

also be copying the current setup of the double dimmer switch, why would this not work?

No reason, but I fear that if it doesn't you won't know why...

We have managed to get it working so that we can have one set on in each room, but not get both on together.

A multimeter is just as important a tool as a screwdriver - in fact more so, as you might just get away with a pen-knife for the screws. If you had one you could trace the wiring, identify the permanent and switched lives, and work out what should go where...

 

[Taylortwocities]

Examine your old switch and see how the terminals are marked.
Examine your new switch and see how the terminals are marked.

You will then have a clue as to where you have gone wrong!


Likely scenario:

Old switch New

L1 ............. C
L2 ............. L1
L3 ............. L2

Get the idea?

 

[shazza]

Examine your old switch and see how the terminals are marked.
Examine your new switch and see how the terminals are marked.

You will then have a clue as to where you have gone wrong!


Likely scenario:

Old switch New

L1 ............. C
L2 ............. L1
L3 ............. L2

Get the idea?

on old switch we have

L1, L2 and L3... written on both blocks

on new switch it has

Way1, Way 2, common written on both blocks

are you sayinq L3 = Way2 ?

 

[ban-all-sheds]

L3 = Way 2
L2 = Way 1
L1 = Common

 

[shazza]

L3 = Way 2
L2 = Way 1
L1 = Common

ah-ahh.... think that might be the solution... will let you know!

Thanks!

 

[ban-all-sheds]

Shall we revisit #4?

 

[shazza]

L3 = Way 2
L2 = Way 1
L1 = Common

ah-ahh.... think that might be the solution... will let you know!

Thanks!

It works! Thank you so much.

Also - with a metal dimmer switch is there anything to be careful with on the wiring?

 

[ban-all-sheds]

The circuit must have an earth conductor, which actually works, i.e. there is continuity of it all the way back to the CU.

 

[Taylortwocities]

And the earth conductor must be connected to the earth terminal on the switch front plate..

 

[shazza]

And the earth conductor must be connected to the earth terminal on the switch front plate..

the casing box is metal, but there is no earth wire. presume deffo not to use a metal switch?

 

[ban-all-sheds]

No.

Nor any Class I (non-double-insulated) light fittings. It might simply be that the idiot who installed the cable cut the earth back, but even if there's enough slack for you to get at it and reconnect it, do you really want to gamble your life on him not being idiotic enough to have done the same elsewhere?

Unless you get an electrician to confirm that you have a fully functioning earth throughout your lighting circuit you must not use metal switches or Class I lights.

 

[shazza]

No.

Nor any Class I (non-double-insulated) light fittings. It might simply be that the idiot who installed the cable cut the earth back, but even if there's enough slack for you to get at it and reconnect it, do you really want to gamble your life on him not being idiotic enough to have done the same elsewhere?

Unless you get an electrician to confirm that you have a fully functioning earth throughout your lighting circuit you must not use metal switches or Class I lights.

thanks! ...back to the shop for a Plastic double dimmer switch.