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. 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 on
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.