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Trying to replace a simple lighting fixture, but the wiring defies comprehension

Trying to replace a simple lighting fixture, but the wiring defies comprehension

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  #1  
Old 07-02-17, 01:47 PM
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Trying to replace a simple lighting fixture, but the wiring defies comprehension

Okay. I have a house in Pittsburgh built in 1965. There's a basement, a first floor and a second floor. 3 bedrooms and a bathroom on the second. Everything on the second floor is controlled with a single breaker. Also there's a stairway from first to second. At the bottom of the stairway in front of the front door, is a ceiling light. At the top of the stairway above the second floor landing, there is another ceiling light. At the top and the bottom of the stairway, there are double-switches. You can control either the top or bottom hall light, from either the top or the bottom of the stairs. If you turned on the first floor hall light with a switch at the bottom of the stairs, you could then ascend the stairs and turn off the same light with another switch at the top of the stairs, got it? Also, the lighting fixtures, in case it matters, were those single-bulb acorn shaped clear crystal things. OK, so..

One day the light at the top of the stairs just stopped working. I said okay, needs a light bulb, right? New light bulb in, nothing happened. Checked the switches: top and bottom of the hall both still turned on/off the light at the bottom of the hall. Neither level switch would turn on the upstairs light. Checked all the breakers, everything as it should be. Alright, I thought, maybe its the fixture itself. Could happen. IDK how old it is. I goes down to the Orange Box, and I buy two brand new fixtures of a more modern style, this one.

First, I replace the one downstairs (which was still working perfectly). No issues. Two caps. Two wires, one hot, one not, flawless replacement, takes me 5 minutes. Then I go upstairs...

I remove the old fixture and there begins my astonishment. First of all, there are THREE (3) end caps in there. I wasn't expecting that. Here's what's in this rat's nest:

One end cap has a single black wire in it that registers as hot. One of the fixture's wires was in a cap with this.

Another end cap has THREE tan colored wires in it that register cold. The other of the fixture's leads was in here with these 3 very stiff wires.

Then there is a THIRD end cap, which was tucked up into the wiring box. This cap has THREE black wires AND a TAN wire and registers as hot. It was not connected to the lighting fixture.

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I could not make sense of this, since I've never opened up anything else in this house and ever seen more than a hot, cold, and ground. So, I'm thinking, maybe it has something to do with these double switches in the stairway. Don't overthink it. Just ignore it. But then, why aren't there 9 wires inside my downstairs light wire box too? Idk... anyway

So I wire the new fixture up just as the old one was, hot to hot, cold to the three colds, which was extremely hard and required a little stripping, and the ground. Added a light bulb, turned on the breaker... nothing. Okay, I had a CFL bulb in there, maybe the surge of the power coming on blew it? I put in a new bulb I just tested in a lamp and I know it works.. nothing.

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I think, maybe all my wires don't touch. Re-did both connections, especially concentrating on the 4 wires in the cold cap (including the fixture). Did that one several times, in fact, just in case. Nothing.

I even once tried reversing the wires from the fixture and putting them in the wrong caps, just in case, I don't know, China got its colors wrong. No dice.

Only thing I haven't tried (but have thought of) is swapping out the known-good new fixture from downstairs to upstairs, just in case I have the coincidental bad fortune of buying a bad fixture to try to install (but those odds seem kinda remote).

And as a final thought, I never really did figure out why that old fixture just up and quit working to begin with. But I have a really nice, two-year old EATON breaker box that is really good, perhaps too good, at telling me if I have any issues, and so far it has said nothing.

Oh, and so far as I know, nothing has ever been there but a single light (i.e. no fan, wouldn't even fit there).

Anybody know what the hell's going on here? Thoughts? And apologies, don't know why a couple of my pics went sideways.
 

Last edited by ray2047; 07-02-17 at 02:21 PM. Reason: Delete unneeded images, crop and enlarge remaining images.
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  #2  
Old 07-02-17, 02:12 PM
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Welcome to the forums.

Overstuffed/overfilled box but very common wiring.

You have four cables in that box.
1) power feed in
2) power feed out
3) power feed out
4) switch loop. The switch loop cable is the one where the white wire connects to the three black wires and the black wire is the one that goes to the light.

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Basic switch loop circuit.
Your two power feed out cables are connected directly to the power feed in cable.
The switch loop cable goes to your three way switches for ONE light.

If this light is not working.... I'd look to a three way switch problem.
 
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Old 07-02-17, 02:25 PM
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Note if you replace the switches be sure you mark the wire connected to the common of each switch. Common will be the odd colored screw, usually dark gray. Note you must go by screw color when installing a new switch not position on the old switch because common may be in a different position on the new switch.
 
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Old 07-02-17, 03:01 PM
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If the problem was the switch, say the one upstairs, would that make it so that neither switch (first or second floor) would turn on the light upstairs? And still allow both floors to turn on the first floor light?

Also, I am confused by your statement that there are four cables. I'm thinking you mean the sources? As I mentioned there are at least 8 wires total in there. But plodding on, what i understood was that I should ignore the third cap with the three black and one tan in it, as that is the switch loop, which means that the light should correctly be wired with one wire in the cap with the black (hot) and one in the three tans (neutral)..? Because that is the way the previous fixture was wired, and that's the way I re-wired the new one.

So bottom line, your advice is the switch? Then I refer you again to my initial question about the switches, because I couldn't figure out why, if the switch had gone bad upstairs, it didn't work downstairs either, but yet the downstairs light still worked fine from either floor level.
 
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Old 07-02-17, 04:45 PM
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If one part of the switch on a traveller has gone bad the switch may operate properly in the other position.
 
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Old 07-02-17, 04:49 PM
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Also, I am confused by your statement that there are four cables. I'm thinking you mean the sources? As I mentioned there are at least 8 wires
A cable consists of at least two conductors, grounds aren't included in the count. Eight wires would be four 2-conductor wires.
third cap with the three black and one tan in it,
Those are wire nuts not caps. Those are old white wires not tan wires.Cables don't have tan wires

Here is another way to diagram the basic switch loop Pete posted.

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And here is a typical 3-way switch basic switch loop.

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Examples of 2-conductor cable and 3-conductor cables.

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