Peculiar old wiring for light fixture


Old 01-21-15, 04:38 PM
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Peculiar old wiring for light fixture

I have a room with only 1 light fixture. And that has never worked (since May when I bought the fixer-upper). I finally got to the point of replacing the fixture. HOWEVER, the new fixture doesn't work either. Hence, it seems the wiring is wrong.

As I look at the wiring, I see something very odd -- at least, so far as I know (which is almost nil). I'll attach a photo, but the description probably explains it better. Here is what pre-existed inside that light box:

There are 3 house wires entering into the box. Let's call them HW1, HW2, HW3.
They have the following connections (direct contact via wire nuts):
(a) HW1 white wire with HW2 white.
(b) HW1 black with HW2 black with HW3 white.
(c) bare ground wire from all 3 are wound together.
(d) light fixture white was connected with (a).
(e) light fixture black was connected with HW3 black.
(f) light fixture ground was connected with (c).

I had typed up most of this before I (finally!) found my multi-meter. Now I can add that when I turn on the circuit at the switch box, I measure about 10V between HW3's black and (a). [It sometimes seems constant about 11V, sometimes wavers around 7V-11V.]

So, my guess is that connection (b) is all wrong. I should probably take the HW3's white out of that connection and put in HW3's black.
Then I could put in the light fixture's black as well.
And put the light's white in with (a) -- and HW3 white.

Does this all make sense?

BTW, why would there even be 3 house wires going into the box? Is that just where they branched out to a receptacle box? There's a likely candidate receptacle further out along that wall, which apparently would be the end of the line.

In case it matters: the house was begun in 1938, but this is in an addition whose date I don't know. I'm guessing 1950s, but it's a blind guess.

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Old 01-21-15, 06:09 PM
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I would start by turning off the power,opening all those splices,strip back that cable insulation, turn the power on and with your Multi meter test between black and white of each cable until you find 120 volts, put wire nuts on those two wires,switch your meter to Ohm's,and test between the B&W of the remaining cables,make sure the switch is ON ,when the meter 0's out that will be the switch leg,that white will connect to the 2 blacks ,wirenut, 2 remaining whites will connect to the fixture white,the black from the fixture connects to the remaining black,make sure the power is off during this process.
Grounds will all get connected together with the fixture ground and with a pigtail connected to the box with a ground screw.
Old 01-21-15, 06:18 PM
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You have three cables.....
A feed in. (HW-1)
A feed out. (HW-2)
A switch loop. (HW-3)

The black from HW-1 and the black from HW-2 go together with white ? from HW-3. This connection carries hot in on 1 and out on 2 as well as hot to the switch on 3.

The white from HW-1 and the white from HW-2 and the white from your light fixture all get connected together. This is your neutral connection.

The black from HW-3 goes to the black of your light fixture. This carries switched hot back from your switch.

With a switch loop.... the white should be remarked a color other than white or green as it is not a neutral.... it's a hot wire.
Old 01-21-15, 09:36 PM
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OK... hmm. So it looks like the wiring is correct, after all! Glad I asked.
I'll check the switch's connections & see if anything is amiss on that end. If not,, I'll test as suggested. (But tomorrow. It's dark & cold now!)
Old 01-29-15, 12:06 AM
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Conclusion is: it was all wired correctly. The problem was (& is) that the wire to the switch is not intact. Everything else is fine.
My guess is that the switch loop's wire was probably chewed through by rats. Durn critters. I'll have to go up into the attic to inspect the wire, no doubt. (But... right now, that's a bit of a challenge. The stench of rat feces is overpowering. Did I mention that the previous resident was a renter who left trash everywhere? Rats. It'll have to be cleaned out sometime when the weather's better. I can inspect the switch loop after that.)
So for now, only table lamps in that room.
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