Edit – Solved. Thank you @Harper – Reinstate Monica!
A light connected to the same breaker was wired incorrectly upstream from the problem receptacle.
I think I might be a little over my head trying to DIY some electrical work in my 60's home. I am trying to replace my old 2 prong receptacles with GFCI protected receptacles following this Sparky Channel video https://www.youtube.com/watch?v=16KObgI44UE. To find the most upstream receptacle in the circuit, I removed all the receptacles (7 on this breaker, also 3 lights), capped all the wires, then tested with a non contact tester to see which line was still hot.
Oddly enough, 3 of the boxes still had hot black wires. 3 of the boxes also have no load wires (so only 1 set of black and white wires) and in one of those boxes both white and black wires are hot. There are only 2 wires in this box and both of them are hot. How?
I tested again with a (cheap) multimeter and got 120v from black to the metal box and also got 120v from white to the metal box. I am not knowledgeable at all about how to use a multimeter so not sure if that proves anything. The old receptacle was wired normally (white to neutral, black to hot) and did not work for as long as I can remember.
I plan on hiring an electrician eventually to take a look at this but unfortunately I cannot afford it at the moment. In the meantime, I plan on capping the 2 wires and covering it with a blank wall plate. Pretty curious as to how this happens. Greatly appreciate any enlightenment!
Best Answer
Wait, are they metal boxes? Are the wires in conduit or AC cable? The conduit/cable is a valid ground path.
Your neutral is that way because neutral is disconnected somewhere between this point and your panel. Somewhere on this side of it, you have a load plugged in, and it's pulling the voltage up toward 120V.