Don, after searching the Bentley I found what I think is your problem.  On
page 97.140 it shows a 50 amp fuse for the AC system that is not in the fuse
panel and seems to also control the juice going to the exciter wire of the
alternator (why I don't know).  I am only guessing but I think this fuse is
in the rear of the van on the driver's side where the refrigerant lines go up
to the evaporator (inside your rear cabinet).
Hope this helps.
Ken Wilford
Van-Again
John 3:16