I have a cable inside the wall box of a light switch in the UK and it is not connected to anything but it is live. The wires are sitting inside plastic connector/strip. Upon opening up the connector, I found that none of the wires were stripped back. Black wire reads about 150 V ac to earth on the same cable and I believe the reason for this is poor earth connection on the other end at junction box. Should I remove this "unused" cable while I still have my floor boards lifted for safety reasons?

old junction box

light switch box

  • 6
    Are you saying that the gray cable containing a red & black wire is the "random" one? Odds are good that it serviced something in the past that has since been removed. There's probably no great value in removing it, but knowing where it goes (and figuring out why it only measures 150v to... ground maybe?) would be a good thing. Then label it for future use.
    – FreeMan
    Jun 18, 2023 at 12:16
  • Depending on your meter, the 150V reading may be just induced voltage from actual live conductors adjacent to the cable and a meter with high input impedance not drawing any current to speak of.
    – Ecnerwal
    Jun 19, 2023 at 0:27
  • Thanks for reviewing. Yes black wire to earth on the same cable shows 150 V.
    – Dai
    Jun 19, 2023 at 13:18
  • Added picture of some kind of old junction box? This is where the cable is leads to
    – Dai
    Jun 19, 2023 at 13:22
  • 1
    Which wires aren't stripped, and why would you expect them to be? All the ones that need to be stripped that I can see, are.
    – kreemoweet
    Jun 19, 2023 at 16:44

1 Answer 1


If the two wires haven't been stripped, and have been shoved into a terminal block, then they must be spare wires. Presumably they used to do something. By shoving them into a terminal block, it keeps them safe, so they can't touch anything else.

If you're certain they are no longer needed, then you could remove them, but you would have to work out where they go first.

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