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I am by no means an electrician, my experience does not extend past swapping old light fixtures for new. We just moved into a house that was built in 1907, so I'm not surprised by anything I've come across thus far, however I've heard mixed answers from people I know about this one.

I am trying to just change our dining room light, and upon removing the old fixture, I discovered just 2 wires. Both are covered in a cloth which I've read was common way back in the day. The fixture itself was mounted directly to some joists I'm assuming, as I see no box; only two holes through the wood where each wire comes out. One is wrapped in a thicker material further back.

It would obviously be best to hire a professional to rewire this I'm sure, but is there any clear and present danger to maybe just getting a pancake box and mounting it to the joists? And what's the best way to identify which wire is which, as the old light fixture's wires weren't color-coded either.

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  • This is probably better answered at the Home Improvement StackExchange forum. For the wire ID, can carefully use a multimeter (voltage mode with the appropriate AC range selected) vs a reliable earth connection, which this vintage of wiring probably lacks. Obviously don't touch it, or the conductive parts of the probe, when energized. Getting shocked on a ladder is a good way to get seriously hurt. PS - once you figure out the pattern, prepare for the possibility that the wiring is done backwards in some places! I've had that surprise in an old house.... – Pete W Mar 22 at 19:38
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    If the place is a rental you better call an electrician, legally you can be in trouble if a tenant is looking for excuses. you can establish the polarity using even a testing screwdriver tool. then you need to find the breaker by toggling all the subpanel breakers one by one. This may give you a chance to replace the bad breakers too. – kamran Mar 22 at 20:41
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    The last time I saw actively used cloth covered household wiring was in the 1960s when my parents bought a very old house. They had the entire house completely rewired to make it safe with the electrical wiring standards of the time. I recommend you do the same. – Fred Mar 23 at 3:00
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The big thing is figuring out which wire is switched hot and which wire is neutral. Note that it is possible, due to messed up wiring, to have some other combination, such as hot and a switched neutral, which would not be a good thing.

Use a non-contact tester to:

  • Verify that both wires are "dead" with the circuit breaker (or fuse) off. If not, stop and ask a question. (There can be false positives, but really shouldn't be on a simple fixture connection, as opposed to wires in a box with a bunch of other wires).
  • Turn on the breaker. Verify that both wires are "dead" with the light switch off. If not, stop and ask a question, as you may have a switched neutral.
  • Turn on the switch. Identify which wire is hot. This wire is the switched hot. The other wire is the neutral. Mark the neutral wire with white tape.

Turn off the breaker. Wire nut the light fixture hot (typically black, but could be any color except white, green or bare) to the switched hot wire. Wire nut the light fixture neutral (should be white) to the neutral wire. Turn on the breaker, test.

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    I would also suggest adding short pigtails between the cloth covered wire and your fixtures wire using short lengths cut from the black and white wire inside some spare NM cable (of the same wire gauge). I have often found the old ends to be a bit brittle and you may not have much spare wire length left if it breaks on you a few times. The new pigtail will spare your old wires some abuse the next time you work with this fixture. – blarg Mar 31 at 16:22

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