trader_4 wrote, on Mon, 22 Dec 2014 08:21:13 -0800:

I've never seen a furnace where it's not obvious where the power comes
in. I'm beginning to agree with Stormin.

OK. Fair enough. I haven't looked hard enough mainly because
I really don't think the problem is a reversed polarity on the
AC circuit.

First off, the thing is AC, so, "most" AC items don't care
whether the hot or neutral are reversed anyway; but more
importantly, nothing was done to reverse the hot and neutral.

Looking at my pictures, clearly the line voltage comes in right
at the middle, from the overhanging flexible metal BX cable:
https://c4.staticflickr.com/8/7516/1...72dc89861a.jpg

So, I'll pop off the cover of the box on the inside of that
connection - but - really - that will just tell me what I already
know must be the case - which is that the AC "line voltage" isn't
reversed.

But, I'll check it - and report back - with pictures.