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The floodlight in the back of my house doesn’t work, I also have a handful of mystery switches so I figured I would open up the fixture and make sure it was wired right (or at all, I’ve found a handful of switches and fixtures that just weren’t connected). I opened it up to look at the wiring and I found something very strange. How can I understand what is going on here?

Obviously because I can’t draw white lines with white I did that with yellow lines. Also as you’ll see from the schematic, three power lines come into the electrical box. And apparently (checking with my multimeter) there is actually power coming through on the white wire, not black. Very strange. Also those two unterminated white lines didn’t even have wire nuts on them, it was just insulted wire. So I stripped them and covered them with wire nuts (not in the photo) to make sure there was no possibility of any arcing.

I’ve checked the voltage going through the white and black lines that connected to the light were only carrying about 5V of power so I figure that’s got to be phantom voltage. When I connect the hot (white) wire with other wires I get about 60V, not 120.

How can I explain what is supposed to be going on here?

I’ll probably have to call an actual electrician to look at this but what are some potential troubleshooting that I can do to fix it and/or figure out what is supposed to be done correctly?

Here’s a photo of the wires:

enter image description here

And here is a drawing of the circuit:

enter image description here

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  • What's in the box where the switches are, are the two white wires uncapped there? – JACK Jul 29 '20 at 13:36
  • @JACK I may need to trace out the wires. I have 3 mystery switches all on the same breaker. Two of them are connected to power lines, and another is disconnected. What’s strange here is that the uncapped white lines are in different power lines. Not the same one – Jason Jul 29 '20 at 13:38
  • @JACK to explain more, the disconnected switch does have two unterminated wires but they are part of the same NM cable whereas here they are part of different NM cables. – Jason Jul 29 '20 at 13:42
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    I did run into something like this years ago: the cable on the left was your always hot with neutral tied to light, middle cable went back to the switch using only the black wire to power switch, the cable on the right went to the switch and only used black as the switched hot and connected to the fixture. It was probably a novice who heard you can't use white as a hot so ran two cables and capped whites. – JACK Jul 29 '20 at 14:42
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    @jack I agree it could be a feeder to other lights or outlets also. I like keeping my outlets and lighting separate but on low budget jobs they get combined to save wire. – Ed Beal Jul 29 '20 at 15:18
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To me it looks like you should have a feeder hot and neutral, once you figure out the feeder turn the power off and correct the light fixture. a second location could be an outlet or a second switched fixture

last a switch leg but this whole mess was mis wired at some point,

You identified the feeder From above , the white hot should be going to the switch (Connected to the black feeder). the black coming back from the switch Connected to your light’s black wire and the light white to the feeder white.

Disconnect the one you don’t know what it is turn the power back on and look for a receptacle that is now dead , or another light or switched light it could even be both.

If the cable that is disconnected controls both receptacles and switched lights connect to the feeder black to black, white to white and grounds together.

If the disconnected cable goes to a light or receptacle you want to be on the switch connect the ground and neutral the same as the last step but move the black wire of this cable to the switched black& light’s black

That should cover every option I believe.

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