On Thursday, October 23, 2014 7:36:10 AM UTC-4, trader_4 wrote:
On Wednesday, October 22, 2014 11:46:46 PM UTC-4, wrote:
Did you check what the other end of the thin bare wire was connected to (to dangle a preposition)?

And what size that "thin" wire actually is? I think by code it has to be
the same size as the branch circuit conductor, but not sure on that.
Meaning you can't use a thin wire.

In a AC (BX) cable there's a thin metal strip that runs inside the armor so provide a grounding path. it isn't anywhere near as large as the current carrying conductors, its primary purpose is to bond together the armor to prevent a condition where if it's flexed enough the current isn't taking a spiral path.

Now current production AC will have a separate ground wire within it, although as far as I know using grounding type receptacles on old AC is still completely acceptable.

nate