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I recently bought a home built in 1908 and I've found some funky electrical issues - such as the entire main floor on one 30 amp circuit. This morning I went down to the bathroom on the main floor and the light switch plate (light switch on top, outlet on bottom) was very hot with a slight smell of burning. I cut the power and say that the back of the switch/outlet was a bit melted. There were 2 wires coming in and 2 wires going to somewhere (assumed to be the light).

Also saw that some of the wires (old cloth wrapped type) were losing their insulation a bit. Since the wire was in a metal conduit (i.e. pipe, with a metal box holding the actual switches) I cut some of the piping away so I could access the wires and re-wrap them.

When I went to test the wires to reconnect everything I found that the 2 wires coming in are BOTH hot when I touch one sensor to one wire and the other sensor to the metal pipe covering the wires coming in. However, the circuit would not complete (i.e., my tester didn't light up) when touching one of the hot wires to either of the wires going out (presumably to the light) or one sensor to the hot wire coming in and one sensor to the pipe covering the wires going out.

Unfortunately this has also knocked out the electricity on my entire main floor (because it is all one one circuit) and it seems that no combination of reconnecting the wires is working.

So I'm quite confused - there seems to be no neutral coming in and I cannot restore power to the rest of the circuit.

Any ideas? Even if I can get to the point of restoring electric to the rest of the floor and calling an electrician that would be great.

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    What "sensor" are you using? A multimeter? What setting were you using? What was the actual reading? Can you not just hook up a new switch exactly the same way the old one was?
    – longneck
    Commented Jan 19, 2015 at 3:29
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    Honestly, calling an electrician sounds like the safest bet. Do you recall which wires were connected to the switch? Were any of the wires connected directly to each other? It sounds like the box was a junction passing current through to the rest of the floor. Which seems a little odd if there's no neutral in the box. But if the entire floor is on one 30A breaker, which is also a little odd, then it's not surprising that the hot wire passing through that box is paired up with a neutral elsewhere on the circuit, somewhere downstream. Maybe a good time to look at rewiring... (1908?) Good luck!
    – Craig Tullis
    Commented Jan 19, 2015 at 3:35
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    You should definitely contact an Electrician. By your account you have a potential fire hazard, which in my book warrants professional assistance (not the help of some random Internet folk).
    – Tester101
    Commented Jan 19, 2015 at 13:40
  • Is this a regular or 2-way switch?
    – Ariel
    Commented Jan 19, 2015 at 17:58
  • @longneck I was using a basic voltage tester, like this one: homedepot.com/p/…
    – jnk7711
    Commented Jan 19, 2015 at 18:37

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Belatedly -- from the OP's description, it appears that the original wiring was quite naughty and used the metal conduit as a neutral. This'd explain the lack of a return current path once the conduit was cut back to repair the wiring insulation, which is also a no-no as you probably won't get it back together again without an excessive amount of work.

Not only does the OP need an electrician, the OP needs to warn their electrician about this lest they zap themselves unwittingly! (A family friend of mine who is an electrician encountered a similar issue, only finding out when a conduit fitting arced as he went to repair it.)

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