dimmer switch no common

[Zaffy]

The push in button on my double dimmer switch wore out.
It controls halogen lights the other button controls one bayonet light bulb.
I unwired the whole thing, taking careful attention to mark where the wires go.
I bought a new module and rewired it in exactly the same way.
The module that I did not replace, and lights just one bulb, still works fine.
However the new module still does not work, it is a Richmond Grid500 Tungsten / low.
The original module was a Home Automation product 60-400w.
The new module has just two wires going to it = Brown to L1 and Red to L2. There is no common wire.
When I rang the manufacturers they said there has to be a common wire going to it, or it cannot possibly work.
The lighting has been in place ten years and has worked fine, it was purely that the push in button did not click anymore.
I repeat, there are no spare wires, just L1 and L2. All I did was simply swap one module for another.
The old Home Automation module on the left side of the dimmer module that works fine is wired thus = Blue to L1 and Red to L2 and yellow to common. The two earth wires are attached to the metal outer casing.

[spinlondon]

Are you saying, that there are only two terminals in the new switch L1 and L2, or that there are three terminals, but that you have connected the conductors to L1 and L2 instead of L1 and common?

[Zaffy]

There are three terminals marked C, L1 and L2. But only two wires, one red and one brown.

The other half of the double dimmer, which works fine, has Blue to L1 Red to L2 Yellow to Common.

[spinlondon]

I'll try to put this in simple terms: L1 is live, L2 is also live and C is common.
Both L1 and L2 connect to C, depending on the switch position.
Usually, in the On position, L1 and C will be connected, and in the off position, L2 and C will be connected.
At no point will there be a connection between L1 and L2.
Remove the wire/conductor from the L2 terminal and place it in the C (common) terminal.
Just for your information:
The other half of the double dimmer is switching a light, that should have two switches, one either upstairs and the other down, or one at each end of a room or hallway.
Perhaps you have a room, that has been converted from two rooms.
On that half, any of the wires/conductors, Red, Blue or Yellow, can become live depending on what position, the other switch is in.

[Zaffy]

Thanks for responding.
I felt sure I had marked the module correctly, but you are the third person that has said the wire must go to L1 or L2 and common. So sorry to confuse you.
However, I have tried the other combinations L1 and common and L2 and common but lights still do not work. There is an on/off switch on the other side of the kitchen to control the same lights but this also does not work.
As I have already mentioned, the half of the dimmer that works controls just one bulb and this works fine.

[spinlondon]

What you have is a 2 gang switch, both gangs being 2 way.
When wired for 2 way switching, it is normal to use a cable called 3 core and earth.
The colours used in such a cable are Red, Blue and Yellow. For new cable, this has been changed to Brown, Black and Grey.
As such from what you have described, the half with the Red, Blue and Yellow wires is the side which controls the light with the switch on the other side of the room.
The switch you have replaced cannot be controlling a light with two switches, if there are only two wires connected to it.
The colours that you have described, do not sound correct.
At one switch, you state there is a brown and red wire, these should be black and red.
Is it possible that the brown is a black wire that has been oversleeved?

[Zaffy]

Sorry, the brown wire is indeed black, at a certain angle it looks brown.

To reiterate. Double dimmer module that is okay, and controls one light bulb, has a yellow, a red, and blue wire. That module controls nothing else.

Module that is broken has a black and red wire and controls six halogen down lighters. On the other side of the room there is an on off switch, not a dimmer, for the same down lighters, obviously also not working.

[spinlondon]

As I've already said, the switch you are refering to cannot possibly control the lights with two switches.
It's physically impossible.
The switch with the red, yellow and blue wires has to control it, that's what the three wires are for.
A normal switch, only requires two wires, live in and switched live out.
It is only when you have two switches, that you require an extra wire, so as to allow the other switch to also operate.

[Zaffy]

Thanks for your patience.
Red is in common black is in L1
Still does not work.
Any other suggestions?

[spinlondon]

Do you have any means for testing if a wire is live?