Crumbling insulated wire in old light fixture

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Old 04-13-19, 02:26 PM
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Crumbling insulated wire in old light fixture

Hey folks, this is my first time posting and I have little experience doing electrical work, so be nice! I went to change the vanity light in our bathroom today and pulled the old fixture off only to find a set of old wires with the fabric insulation tattered off and the rubber/vinyl/whatever underneath crumbling off in patches. I suspect this is from running too hot over the years. I've attached pictures of the setup including the bare spots where the wire's coating has come off.

There is a BX cable on the right coming in with 2 wires -- (1) a black wire that just wraps through into the BX cable on the left, and (2) a white wire that connects with a white wire from the BX cable on the left, and to which I presume the light fixture also ties in. The left BX cable also has a red wire, which I assume connects to the neutral on the fixture...? I pulled the old fixture off before observing how the wires connected - I know, rookie mistake.

I'm wondering three things:
  1. Am I right about connecting the light: positive to white BX, neutral to red BX
  2. Would it be an adequate repair to simply wrap the crumbly BX wire with a good vinyl tape like 3M Super 33+?
  3. Is it possible the rest of the BX in the house is a danger? The are are 3 circuits on BX and the rest on more modern romex, but those three must be the original three because the run most of the main floor and a few basement/outdoor auxiliary lights.
Pics attached. Thanks!
 
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Old 04-13-19, 02:53 PM
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Am I right about connecting the light: positive to white BX, neutral to red BX
No. White (or gray) are usually neutral. Red is hot, usually switched, never a neutral.

Would it be an adequate repair to simply wrap the crumbly BX wire with a good vinyl tape like 3M Super 33+?
It's one way, another is heat shrink tubing.

Is it possible the rest of the BX in the house is a danger? The are are 3 circuits on BX and the rest on more modern romex, but those three must be the original three because the run most of the main floor and a few basement/outdoor auxiliary light
Yes, could be dangerous. Note the wire is only rated for 60C and most modern light fixtures specify 90C. If possible I'd replace back to the breaker panel.
 
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Old 04-13-19, 03:02 PM
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OK, I'm correcting my assumptions from what I stated above. I think the connections should be:

BLACK FIXTURE WIRE --> RED SUPPLY WIRE
WHITE FIXTURE WIRE --> WHITE SUPPLY WIRE

Yeah? Eh?
 
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Old 04-13-19, 03:12 PM
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Awesome, thanks! I just adjusted my assumptions based on further thinking/reading to what you stated regarding the red wire.

The problem with rewiring the BX back to the panel is that it would involve literally the entire main floor. This seems like a pretty intensive or expensive operation. But I see what you mean.
 
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Old 04-13-19, 03:23 PM
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I would recommend using heat hrink tubing instead of tape. Will be much easier and you can push it in much deeper than tape.

Since you have black wire loop into another hole, I wonder if you have conduit instead of BX cable.
If that is the case it would be possible to change wires out.

As long as you don't move wires around your existing wiring should be ok. When replace light fixtures use heat shrink tubing for better insulation. Most are rated 100C+
 
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