I have a length of two Ethernet cables running upwards from a socket. I vaguely know where they are (+-10cm), and I want to fix a Vesa mount to the wall near their route, so i need to trace exactly where they are, so I won't drill through them.

What would be the best way to find them? Cables are run under plaster, on a brick wall, and since it's freshly finished,I really want to avoid digging them up.

I thought of connecting 230V to them, and use normal wire detector, but there has to be a safer way to do this.

  • So, are they in plastic conduit embedded in plaster over brick?
    – jay613
    Apr 29, 2021 at 10:35
  • @jay613 They're embedded directly in plaster, without any conduits. If replacing a cable wouldn't require repainting the whole wall, i would just risk it and drill :) Apr 29, 2021 at 10:37
  • 4
    I'm no expert, but 240v through the tiny wires in a Cat5/6 cable will help you find them very quickly. You'll be able to trace the line of char right up the wall. NOT recommended.
    – FreeMan
    Apr 29, 2021 at 10:43
  • make sure that there is nothing connected to the lan cable ... advise everyone in your house to stay away from lan jacks ... connect only the hot wire from 240 V ... then use a wire detector ... you can also buy a tracer tool that does exactly that, without the 240 V connection
    – jsotola
    Apr 30, 2021 at 1:47

2 Answers 2


There are digital stud finders that you use with your phone and the hype from their advertising implies you can see anything through anything. I can't vouch for them but it's worth a look.

There are wire tracers like the toneout boxes the phone company used to use. There are cheap ones. The receiver does not need electrical contact, it's meant to work through the wire insulation but I don't know how far through plaster it might work. Maybe worth a try.

Many VESA mounts are horizontally adjustable on their mounting screws so perhaps you could just drill outside the 10cm band and still get the result you want.

  • 1
    For the installation method here (wires "chased" in plaster, not very deep) a standard toner or "fox&hound" set should work fine. One box puts tone on the wires, the other detects it.
    – Ecnerwal
    Apr 29, 2021 at 14:01

The best way to find them is to run a line level from a nearby wire. If you can find a nearby surface-mounted junction box, simply press either of the leads into the one wire in the box and it will be a perfect line level for locating wires. Otherwise, you can use the wire of a convenient neutral wire to do the same thing, or you can use a voltage detector to locate the hot wire.

  • 2
    Can you define "a line level" for those who don't know what that is? What, exactly, does "simply press either of the leads into the one wire in the box" mean? are the wires supposed to stay together from "pressing" them? Should there be a wire nut/Wago/Marrette/other wire connector involved? Please edit your answer to provide more detail - assume your reader doesn't have a clue what you're talking about.
    – FreeMan
    Apr 7, 2022 at 18:00

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