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Need help with replacing 2 gang dimmer switch please

Discussion in 'Electrics UK' started by Laubi, 31 Dec 2019.

  1. Laubi

    Laubi

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    hi all,

    I've tried googling this but cant seem to find all the info I need.

    Im trying to replace an existing 2 gang dimmer switch with a new one I bought.

    I cant wrap my head to why the existing connections are like this and how to rewire the new one.

    All i know is that I can remove the extra eart wire as the new switch is plastic?

    Another quesiotn I have is why the com terminal has no screw for me to fix the wire in. Is it needed then?

    Ive attached photos of the existing wired unit as well as the new one I bought.

    Thanks in advance
     

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  3. terryplumb

    terryplumb

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    The conductors that are in " C" ( common) terminals on your old switch ,would go into the L1 terminals of the new switch. The L2 terminals of new switch would receive the conductors from old switches L1 terminals .

    The black insulated conductor that is not connected to old switch ,should not connect to the new one ,but terminate it in an insulated connector block.
     
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  4. sparkwright

    sparkwright

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    The new switch has a simple wiring diagram on it.

    The markings are different.

    So;
    old com = new L1
    old L1 = new L2

    You need to fit a small connector block onto that unused black wire.
     
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  5. Laubi

    Laubi

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    is there a chance that the ceiling light doesnt work is because that loose black wire was not connected?
     
  6. terryplumb

    terryplumb

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    You have two switches ,what does each switch supply ? Is it one light fitting for each switch ?
    Did the light fitting that is currently not working ,work perfectly well with the old switch ?
     
  7. sparkwright

    sparkwright

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    I take it the short black was not connected to anything?

    If the centre light does not work, maybe it's not compatible with the new dimmer.

    You could fit the old dimmer to see if it works.

    Or you could remove the wires from the dimmer and put together in a connector block just to see.

    Either way, work safely, and make sure the power is off when you experiment.
     
  8. Laubi

    Laubi

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    thank you all for the help. Some more info:

    there are two wall lights (both operated by one switch (left one in the first photo - right one in my diagram)). This is the one that works fine.

    the other is a ceiling light which is operated by the other switch - this is the one that doesnt work.

    I havent done anything to the wires yet. only unscrewed the plate.
     
  9. sparkwright

    sparkwright

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    Ah. The old switch is still fitted.

    Did the light work just before you loosened the switch plate from the wall?
     
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  11. Laubi

    Laubi

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    the ceiling light has never worked sine we moved in (recently). I opened the switch plate and my brain started to hurt so puit it back and went online for help!

    not sure if this makes a difference, but this is in the conservatory.
     
  12. terryplumb

    terryplumb

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    Take pics of wiring at ceiling light that's not working.
    Do you have any electrical testing equipment ,like a multimeter , or twin probe voltage tester ?
     
  13. EFLImpudence

    EFLImpudence

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    Swap the wires in the L1 terminals and see if the lights work/don't work the other way round.
     
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  14. Laubi

    Laubi

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    ahhh I wish I had. But for very specific reasons, it was a nightmare to fit it and of course unscrew it. I can confirm there were 3 wires connecting to the light - green (assume earth) and a neutral (think it was blue) and live (think it was brown).
     
  15. Laubi

    Laubi

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    Im happy to do a trial and error but silly question, as long as switch the power off at the mains everytime I do the works, will testing different wires in different terminals do any further damage?
     
  16. terryplumb

    terryplumb

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    So this light fitting is one that you have fitted ,was there a previous light fitting there that was working ?
     
  17. Laubi

    Laubi

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    Sorry, yes, there was previously a different ceiling light which has never worked since we recently moved in. I fitted a new one to see of the light was the problem but also we didn't actually like it.
     
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