Live & Dead Wires in Light Switch

Discussion in 'Electrics UK' started by Jetheat, 14 Jan 2021.

  1. Jetheat

    Jetheat

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    I opened up my perfectly working 2-gang switch in order to install a new smart switch.

    After plugging the wires into the wrong terminals a couple of times, I realised that a couple of wires were not showing any current (on my electrical screwdriver).
    I probably did something to cause that (pls don't flame).

    Out of the wall, there are two sleeves. Each sleeve contains a blue wire and a brown wire, thus making 4 wires, plus the earth wire.

    The blue from one sleeve and the brown from the other sleeve don't seem to be showing a current after connecting my new switch.

    Later, after disconnecting the light (or rewiring a different way), the brown showed a current but the blue didn't.

    Nevertheless, the lights don't work at all when I reconnect the old switch, and they stay on permanently when I connect the new switch, but only one gang.

    Any idea what the heck is going on and what I can do to fix it?

    Appreciate the help,

    JH
     
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  3. oldbutnotdead

    oldbutnotdead

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    Upload the picture you took of the back of the old switch wiring before you started changing things.



    Oh thats right, you can't cos you didn't mark the wires.


    First thing, stop messing about with live circuits and stop confusing voltage (which your neon screwdriver will detect with varying accuracy) and current.
    Second thing, go and buy a multimeter. Cheap £7 from Lidl will be fine.
     
  4. Jetheat

    Jetheat

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    here are the images before I started rewiring. The wires were hooked from the bottom of the switch.

    blues in live terminals and browns in X terminals.

    C023F415-E270-4D02-8D82-30266C9B3943.jpeg 2131C7A2-19A4-4658-8DC6-52B69941FEE2.jpeg
     
  5. Taylortwocities

    Taylortwocities

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    That helps. Need a picture of the connections on the smart switch.

    EDIT. the wires going to the dimmer should be brown to L and blue to the X.

    and don’t mix the pairs up. The two in one “sleeve” must stay together.
     
  6. terryplumb

    terryplumb

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    Have you altered any wiring at light fitting/s ,or fitted new light fittings ?
    Did both lights work with the wiring shown in your picture , i.e. is the pic taken before you did any work ?
     
  7. Jetheat

    Jetheat

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    You can see I have tried it both ways. But they didn't work as expected with the smart switch. One set of lights came on instead of both sets and one of the wires showed no voltage in that situation. I couldn't switch the lights off.

    Similar experience when I wired the other way around.

    IMG_3451.JPG IMG_3452.JPG

    Any ideas?

    JH
     
  8. bernardgreen

    bernardgreen

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    It would appear your new switch requires a Neutral as well as Live

    upload_2021-1-14_14-13-50.png

    Without a Neutral the switches will not work.
     
  9. Jetheat

    Jetheat

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    Yes, it was wired that way before I did any work and it was working on both gangs.

    JH
     
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  11. Jetheat

    Jetheat

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    Neutral is optional. It says so on the documentation.

    Also, some circuits don't have Neutral wires, like mine, and it was working.
     
  12. Taylortwocities

    Taylortwocities

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    The two lights that this switch needs to operate. Are they on the same floors in your house, are they on the same lighting power feed?
     
  13. Taylortwocities

    Taylortwocities

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    Interestingly. What make/ model are they?
     
  14. Jetheat

    Jetheat

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    yes, same room.
    two sets of 4 bulbs each.
     
  15. Jetheat

    Jetheat

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    Lightwave
     
  16. terryplumb

    terryplumb

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    Have you altered wiring at light fittings ?
     
  17. Jetheat

    Jetheat

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    I am installing Lightwave all over the house.

    Sometimes i have to wire things differently because of the different terminals on the new switches.

    But I think the current issue is because my screwdriver doesn't detect any voltage from one of the wires. Is that normal?

    JH
     
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