Scott;

I've been retrofitting a stock a/c system into my westy for a while now
so I'm quite familiar with its operation:

1 - yes, the radiator fan is supposed to run non-stop when the a/c is
running.  It's wired to do that.

2- if your a/c is stock and your van is an 88 then you have a different
radiator fan and controlling electronics than most vanagons.  In yours
the rad fan is MUCH larger and it has three stages:  a/c on / low;
medium; and hurricane.  The controlling relays are supposed to be:  One
on the fusebox and one behind the driver's fresh air vent (in the
dash).  Behind the driver's headlamp is the resistor that controls the
low and medium speed - I guess if that got wet or something it could
cause the operation you mentioned...  Otherwise the relays should be
fine.

3 - there are two drain hoses for the water that come off of your a/c
condensor.  These hoses run from the rear overhead unit into the
d-pillars.  If you pull the black vents (on the outside, rear upper of
the van (aka D-pillars)) you'll find the hoses just inside these.  They
may be plugged.  Worse, if your retrofit guy pulled the condensor out of
the ceiling unit (which he should on a retrofit) he may not have gotten
those hoses reconnected thus the water isn't getting outside but is
running down from the overhead unit.  The water tray that sits under
that consensor has its outlet hoses in the front corners of the overhead
unit.  If that appears to be the water's source then it's very likely
that your drain hoses aren't connected...

I could help you more if I knew what model you have (westy or not).  The
non-westy is probably a lot easier to get into that overhead unit.  In
the westy it is close to impossible to work on those overhead units; I
had to pull the ceiling out, the side shelves / curtain rods, the rear
clothes closet, and, of course, the overhead housing.  It's a nasty,
nasty job.

Good luck and feel free to email with questions.

Damian