I’m rewiring an upstairs room so it is separate from the other three rooms and found two wires which are both black and separated from each other. One is hot and the other is not. After tracing it into the attic it looks like the hot was connected to black and neutral to white. After I separated it from the room and hooked it back up none of the light or outlets are working in the whole upstairs. The wire is showing hot when I put my power detector next to it. two wiresenter image description here Here are some pictures that will hopefully help describe what I did. I may end up just running another separate line for the two other rooms up there but this is what I have going onenter image description here

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update 1/14 8:30pm So I did not mention that the only thing I left connected to everything in room 1 was the light in the ceiling but I took the fixture out until I finished the room. For kicks I figured I’d hook the old fixture up and low and behold all of the lights now work, but they are dim and flicker.

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    Something in your post doesn't make sense because you said you are separating this room from other rooms, but you havent explained how. You would need another live circuit properly rated and wired to do what it is you are suggesting. What you've pictured isnt that. It's concerning you traced the wire to the attic but dont know where it is going. Can you provide any before modification pictures, and draw out the circuts so we know what connects where? You need this information as well. Isolate power and test/trace it all out. – noybman Jan 14 '19 at 0:13
  • I ran all new wire for this room, haven’t hooked it up yet. I’m more concerned with the other two rooms that the lights aren’t turning on. I’m asking about the existing wiring that won’t work anymore. I removed all old wiring to this room. The top picture of two wires is what is coming up from the basement that the power is coming from, the bottom picture is where the two wires went to that I pulled out and am no longer using. I connected the two wires to the main supply line in the attic that goes to the two other rooms but they are not working. Hope that makes a little more sense – Ken B Jan 14 '19 at 0:40
  • Maybe these aren't the wires you think they are. With them hooked up and a load plugged into the powered sockets, does the other wire still read "not hot"? – Harper - Reinstate Monica Jan 14 '19 at 1:27
  • I might be tracking in my head what the issue could be but unless you can tell us a detailed before and after we'd just be guiding you to guesswork. You really need a before and after identifying all the changes you made. Obviously a change you made has rendered it not working and if you hadn't traced the A--B--C--D.......Z endpoints of the circuit, then your hot is.... somewhere, and your neutral is ..... somewhere... each circuit connecting to it should be HOT-HOT and not miswired. The fact that it is not working is telling us you detached a hot AND/OR neutral from the live circuit. – noybman Jan 14 '19 at 2:34
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    Do you have a tone tool? You can find them at the big box stores. You really MUST identify the panels hot, and panels neutral start point in the building, then trace it point to point and label it as you go so you know what to connect where. – noybman Jan 14 '19 at 2:41

You may have a 'borrowed-something' (not unusual in old wiring) so you have 2 phases or two neutrals at each place.

My advice is to "invert" the two blacks (you have previously disconnected and reconected).

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