Alternator wiring problem: 1984 4000s quattro

["Hare,Stott (X)" <HAREST@allenbrook.iix.com>]

In an attempt to get stagnant projects moving, I'll query the list on a
nagging problem.

The patient is a 84 4kq which was gutted for lowest probable weight, and had
a 2.3L motor thrown in for kicks.  Somewhere along the line we must have
screwed up some of the wiring harness, as the alternator no longer proves
out during key on, and never begins charging.

We have continuity to the cluster/circuit board on the blue exciter wire.
I'm going to attempt swapping in a known good cluster this week.  But the
old cluster worked fine prior to project beginning, so I don't have high
hopes of a different
cluster making thing better.

What I'd like is suggestion on which circuit or wires to check for a fault.
Alternatively, due to the intended role for this car, instructions on how to
set up a circuit to manually trigger the alternator would be acceptable.  I
believe it is more difficult than just providing power or ground to the
exciter wire, correct?  Avi, Scott, Orin???  Any other electrical/Audi gurus
feel free to chime in at any point.

Thanks!
-S

Stott Hare
85 Callaway 4ktq
84 4ktq (MC conversion in progress)