Mark and David,

Thanks for your posts.

Here is the error in my reasoning.  I measured the alternator voltage as
~13.8, the voltage at the junction under the cover as ~13.2 and the
battery voltage as ~12.6 with the 2 heater blower and headlight load.
Because the drops were approximately equal, I concluded that it was very
unlikely that there were two similar failures and that this was the
expected voltage drop under these conditions.  I didn't do the math.

So tonight I got out my reference books and looked at the wire sizes and
I agree with David, 200-300 millivolts appears correct.

I will repeat my measurements tomorrow with the new battery.  There
exists the possibility that the battery was drawing a lot of current.
If I see the same one volt drop from the alternator to the battery, I
will do the pin technique on the wires and isolate the problem.  I also
can use a DC clamp on current meter to read the current.

I also agree with Mark that adding the wire as VW did for an improvement
in later models would help.  However, my Vanagon has been doing just
fine for 25 years without the modification so I am not ready to make
that addition ... yet.

Thanks again for all of your suggestions.  I'll post in a day or two
with the results of my testing.

Mike