Figured I give an update and solution after all this time.
Seems as though my replacement alternator was junk. New battery and alternator under warranty fixed the issue. As a side note, working at a GM shop has taught me that this happens more than you think. So don't rule it out.
I got two bad remans in a row from Western Auto years ago.
I was told once that all that was done at alternator reman shops was to find one bad part, replace it, paint the housing, and box it up. I'd like to think some basic testing was done before boxing it, but I wonder.
I had a customer in the central US who was buying voltage regulators from us. These chips were intended for automotive applications. It's been a while, but, as I recall, the spec sheet required the user to take a measurement during assembly, and apply a pair of resistors to the circuit. The resistor values came from a table with 5 entries, with the measurement result used to select which of those 5 pairs. (I know, it sounds kind of kludgy; that's what I thought 20 years ago when I first read it.)
Anyway, this customer, who was in the alternator reman business, wanted to only stock 2 pairs of resistors instead of 5, so he wanted a spec from us that simplified the selection down to 1 of 2 instead of 1 of 5. Using this would mean that about 60% of the time, the alternators would be out of spec.
I begged off from helping the guy. And I'm still shaking my head over that one. :dizzy: