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I have an outdoor light that isn't working. I've removed and tested it indoors. It works fine and the bulb is fine.

The wiring that comes from the house consists of two twin-and-earth cables. Power is on the same circuit as the indoor ceiling lights.

Please excuse my amateur diagram. The wiring into the lamp looks like this, with the two incoming cables at the top, lamp connections at the bottom:

   | | |     | | |
   | | |     | | |
X__| | |_____| | |__X
     |    |    |
     |    |    |
     ο    ο    ο
     L    E    N
         💡
  • The earths are entwined and wired into the lamp.
  • The live input is taken from one cable, and neutral from the other.
  • The other two wires (X) go nowhere, but may have come loose!
  • I presume one cable goes to the switch, but I can't be sure.

Is this wiring correct? I inherited it when I moved into the house, but it did work once upon a time.

Is there anything incorrect/unsafe about this wiring that could have stopped the light working?

Possible solution:

If the two loose wires have come apart, and assuming one cable goes to the switch. I am wondering if the following is correct. Below the loose ends (previously marked X) are connected so they complete the circuit via the switch (S).

    (S)   
   o   o     L E N
   | E |     | | |
   | | |     | | |
   | | |     | | |
   | | +--X--+ | |
   | +----+----+ |
   |      |      | 
   +---o  ο  o---+   
       L  E  N       

         💡
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  • 4
    That certainly doesn't look right, but maybe someone with more UK experience will have a better idea. This is near London?
    – JPhi1618
    Nov 13, 2019 at 15:53
  • I am in London, yes.
    – Tim
    Nov 13, 2019 at 16:00
  • I added some more info. Do you think the two dead ends (X) have come apart and should be connected?
    – Tim
    Nov 13, 2019 at 17:27
  • 2
    Normally, one cable comes into the box and another cable leaves to go to the next box or to connect to a switch. When it goes to a new box, all the N's are connected together, all the Es together and all the Ls together. They wouldn't be connected to each other as in your diagram. If the second cable was for a switch the pattern would be a little different, but I still wouldn't expect to have two loose wires left over.
    – JPhi1618
    Nov 13, 2019 at 17:32
  • That makes sense. The second cable must go to the switch then. I'll look at updating my diagram with fewer assumptions
    – Tim
    Nov 13, 2019 at 17:46

1 Answer 1

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Thanks to clues from folks in the comments I solved this by simply connecting the two dead ends together to form the switch loop. They had obviously come loose inside the lamp (possibly through wiggling of cable when lamp angle changed).

With these ends connected, the wall switch ON and power OFF I could confirm conductivity between the previously loose end and the live terminal on the lamp. This gave me the confidence that one of the cables indeed went to the switch and identified the live wire. (no useful colours to go by).

With power ON I could confirm 240V between the live wire and the neutral connection on the lamp, and with the switch ON also I confirmed 240V flowing between the L+N terminals on the lamp and the bulb contacts.

Light now works. Thanks all commenters.

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