old BX wire
Went to replace a crappy looking socket in a 1909 house (painted the room), and found what I now know as BX armored wire. However, yanking out the old socket, I find there is two black wires and one white (with a red stripe) wire. It's hard to tell, but in tracing the cable back to the junction box all three wires are connected to similar BX. However, it looks like the white might be being utilized as a ground wire, as it's the only connection not capped/taped...just left naked.
Everything I read about BX is that it was just two wire (B & W), with the armor acting as the ground. Here, I have to assume one black is hot (which one I don't know), but if the armor is the ground...what's the white doing?
So, is there a procedure or tester that can help me identify hot, neutral and ground?
Re: old BX wire
If the BX is properly secured at both ends you should be able to read 120V from the box to the hot. And 0V from the box to the neutral and ground wires. Wrap an inch of black, white and green tape around each wire to help the next guy.
If the BX sheath is not continuous back to the panel temporarly hook a wire to the neutral in your panel to serve as a ground/neutral reference.
Check in your electrical panel which wire was connected to the ground bus and which was connected to the neutral. And use the same connections at the light. This assumes your wiring was updated properly since 1909.
I suspect the last electrician used one of the black wires as the neutral and the white as a ground.
Good Luck from Columbiana, Alabama