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Replacing Dimmer Switch

Discussion in 'Electrics UK' started by Arbu, 31 Jul 2010.

  1. Arbu

    Arbu

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    I have a two gang dimmer switch. One of the units stopped working (you used to have to rotate it until it clicked to turn the lights on, and then it would rotate freely further to adjust the brightness. It started to just click and not then rotate freely and the lights never came on). So I replaced it and copied the existing wiring arrangement. The replacement works on a push basis to turn the lights on and off unlike the old one.

    The lights on the old unit work fine as before, but those on the new unit don't come on at all. Is there something wrong with my wiring? The attachments on the new (black) unit are marked X, L1 and L2 from left to right. In accordance with the previous wiring I've put one live wire and the connection between the units into this, but it's a bit of a squeeze. Maybe I would do better to put the live wire into L2 instead?


    Old unit:

    New unit:

    Thanks for any help.
     
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  3. holmslaw

    holmslaw

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    ..
     
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  4. securespark

    securespark

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    Have you tried switching on the light that does work, then operating the dimmer that does not?

    If so, does it work?
     
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  5. Arbu

    Arbu

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    A pair of wall lights with ordinary screw in bulbs. They worked OK until the old dimmer went.
     
  6. Arbu

    Arbu

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    Yes, I did try that, and no, it didn't work.
     
  7. electronicsuk

    electronicsuk

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    If you've used the X and L1 connections on the new dimmer then I can only assume it's faulty. You already know that there must be power at the switch plate, as the lamps fed by the old red coloured dimmer are working fine.

    My only other thought would be that someone has done something silly like switching the neutral, which your new electronic dimmer does not support. It's a bit of a longshot, though. This would be easily proved by metering between L and E, which should read around 230v.
     
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  8. sparkwright

    sparkwright

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    You could try removing the wire from L1 and putting it in L2.

    Did the new dimmer module come with instructions?
    If so, the wires you have in X are constant live.
    And the wire you have in L1 go to the lamp.
     
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  9. Arbu

    Arbu

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    OK, I tried removing the wire from L1 and putting it into L2 and this made no difference. The dimmer did come with instructions, which I think I'm following.

    I tried removing the brown wire from X on the new dimmer unit and putting the other brown wire in instead. So, if I understand correctly, this would mean that the non-functioning lights would be on the old (red) dimmer unit which I know works OK. And the non-functioning lights still didn't work when I did this.

    So should I conclude that the problem is with the wiring of the lights and not the new dimmer? Unfortunately I don't have a meter to read the voltage across the dimmer. Do I need a different type of dimmer?
     
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  11. electronicsuk

    electronicsuk

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    Perhaps the problem was never the dimmer, or a problem with the wiring also caused the dimmer to fail. To rule out the switch, turn off the power and check for dead, then link the two brown wires together in a single terminal or piece of choc block. Turn the power back on. If the lights don't come on, there's a problem elsewhere in the circuit. I'd advise being wary with this if your CU is fitted with rewireable fuses, as you could have a short circuit somewhere, and you don't really want to be pushing cartridge fuses back in onto a dead short.
     
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  12. securespark

    securespark

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    Or even rewireables! ;)
     
  13. Arbu

    Arbu

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    The problem with the dimmer was a physical one, i.e. it's just a rotary switch, and this operation no longer works correctly.

    My CU does have rewirable fuses so I think I might be wisest not to try your idea to check the wiring.
     
  14. electronicsuk

    electronicsuk

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    Yup, that's the one!
     
  15. Arbu

    Arbu

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    Here's a picture of the old dimmer unit. I don't know if this might somehow be different from the one I have bought.

     
  16. Arbu

    Arbu

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    The manufacturers, Powersave Lighting, have kindly sent me a replacement and it works fine.

    I seem to have a knack for buying duds. See this post too http://www.diynot.com/forums/viewtopic.php?t=197701. Each time I assume it must be me doing something wrong, because I can't believe that stores really are selling such faulty goods. But, yes, they are.
     
  17. Arbu

    Arbu

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    Well it did work fine, for ten months. Then all my lights on the circuit suddenly blew. On replacing them the ones on the dimmer wouldn't work. On opening up the dimmer the circuit in it is blackened. Hard to know if this is the fault of the dimmer or whether a short circuit has taken out the dimmer. Any thoughts?
     
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