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Our house was remodeled by previous owners, and there is a two wire light switch that is a mystery, it doesn't seem to control any of the wall outlets. I tested the switch with a multimeter to make sure it hadn't failed in the "on" position (it had not). And there is no overhead ceiling light. Suspect the switch goes to a junction box in the ceiling that was covered over. And unfortunately, the switch is on the ground floor of a two story house, so there is no possibility of searching from the attic.

How would an electrician go about finding the terminus of this switch? Have not found any obvious patches in the ceiling which could be hiding the j-box.

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  • Location of the switch in house? Is it on an outside wall or a wall inside the house?
    – crip659
    Commented Nov 10, 2023 at 23:40
  • As of now, it is an inside wall. I have a sneaking suspicion it may have been an outside wall at one point. It is sitting directly on what was apparently the original foundation wall. Commented Nov 11, 2023 at 0:11
  • A magnet stud finder on the wall above the switch might point to a metal junction/light box. If it was an outside wall at one time maybe they had a porch light or maybe an outlet for lights(Christmas).
    – crip659
    Commented Nov 11, 2023 at 0:25
  • You're not alone. I have a couple of switches that don't seem to do anything after a major renovation was done. And no, I don't remember what those switches controlled before the reno, Senior moment!
    – SteveSh
    Commented Nov 11, 2023 at 0:32
  • When I removed a wall in my house, it left a switch that went to an outlet. I clipped the wire in the wall and left the switch there for a while.
    – user177013
    Commented Nov 11, 2023 at 4:59

3 Answers 3

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You may be able to locate a metal junction box using a magnetic stud finder.

Junction boxes in the ceiling often have extra blocking around them to hold them in place. If you can locate the ceiling joists using a studfinder or something like a Walabot, then you can likely also locate the extra blocking (joists will be at at regular intervals, blocking won't). That blocking will give hints as to where the box might be.

You can also put a very small hole in your ceiling, then run a borehole scope through it to look around. Many large hardware stores will rent tools like this to you for relatively cheap. You'll have a few drywall holes to patch, but they should be very small. You may also be able to run the scope inside the wall behind the switch and see which direction the wires are running.

Start your search in the center of the room and work outward. You don't normally see ceiling boxes close to the walls.

You mentioned in a comment that this was likely once an exterior wall. If it was, then there's another option to consider. This may have once controlled an exterior light fixture mounted on the wall or under the eaves. If that's the case, then your ceiling isn't where you should be looking. Try to trace where the wires go and see which direction that leads you.

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The way I'd do it (not being a pro electrician) would be to disconnect the wire at the switch and use a wire tracer. These devices inject a signal into the wire and let you follow it with a short-range antenna.

Wish I knew what happened to the one we had in the family. Trying to justify buying one.

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A very traditional, normal electrician approach (you wanna know where this cable goes - let's find out!) is to rip open the drywall and follow the cable, leaving the drywall mess to be patched up by someone who does drywall later - that's separation of the trades (you don't want drywall repair by an electrician - you'll pay too much for a bad job of it...)

You can, of course, save on the electrician part of this by ripping it open yourself, or do both parts yourself; or you can decide that it's really not all that important to you where that mystery cable goes after all.

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  • Cue The Gas Man Cometh, Flanders & Swann.
    – keshlam
    Commented Nov 11, 2023 at 18:11

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