2 way dimmer switches (again)

Sorry wasn't in y/day...ok can you confirm if this is how it should be....at the switch the single red and black wires should go in to L1 and COM, and it doesn't matter which. The other wires are ok as they are.....then at the light all the red should go in to the loop terminal on their own the switched live (black wire) goes in to red connection and the rest go into the black. The last thing...how do you work out which is the Switched Live (black) wire??????
 
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alix said:
Sorry wasn't in y/day...ok can you confirm if this is how it should be....at the switch the single red and black wires should go in to L1 and COM, and it doesn't matter which.
Yes.

The other wires are ok as they are.....then at the light all the red should go in to the loop terminal on their own
Yes.

the switched live (black wire) goes in to red connection
If by that you mean the live terminal on the light, yes.

and the rest go into the black.
If by that you mean the neutral terminal on the light, yes.

You won't forget to put all the earths into the earth terminal, will you?

The last thing...how do you work out which is the Switched Live (black) wire??????
Two ways.

1) With the power off - use your multimeter on low resistance or continuity setting to see which red/black pair get connected together by the switch.

2) With the power on - turn the switch on and use your multimeter on 240V AC (or higher) to see which black registers ~240V to earth, or which one registers 0V to the reds, or, if there are 3 blacks, by eliminating the two which register 0V between them.
 
And don't forget to put a red/brown sleeve on the switch live in the switch side and the rose side.
 
Can anybody help

I have fitted 2 new dimmer switches to old light, perfect no problems turns on and off and even dims have now tryed to fit new light but i get lights permanatly on or nothing at all. on rose there are 3 red 3 black and 3 green on new light there is 1 brown 1 green and 1 blue the light is in the living room and has a switch at each end of the room PLEASE HELP
 
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A common mistake to make is to connect all the blacks into the same block thinking they are neutrals, one of them is likely to be switched live. Firstly turn off the power and double check it is off.
You will need to remove the dimmer switch for this light and replace it with a normal switch (this dimmer is probably broken anyway).
With a multimeter set to ohms range, separate out all 3 cables at the rose and check across the black and red wires on each cable individually whilst someone operates the switch. You should see the resistance go from high to low as the switch is operated on one cable. This is the switch wire, you now need to sleeve the black wire red to signify it is a switched live. This black sleeved red wire connects to the live in the light (brown), the other two blacks connect to neutral (blue) and the earths connect to the earthing terminal. The three reds need to connect together in a separate piece of block. This should hopefully sort out the wiring, as you have almost certainly connected the dimmer switch across L&N it is likely to have blown, hence you will need to replace it with a new one.
 

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