As I remember, the fans are primarily the radiator fans and the A/C is
simply "tagging along for the ride".  However, I feel sure the fans are
controlled by one of the relays which turn the fans on and off depending
on the temperature of the radiator water/antifreeze.  And if you look at
the piping end of the A/C condenser, you will see three "gadgets" with a
pair of wires coming from each.  These are limit switches which control
both the fans and the compressor clutch.  When pressure is low, the fans
are not turned on by the a/c and are controlled only by the water temp.
When the a/c pressure rises, one of these switches overrides the water
temp relay and turns on the fans, regardless of the water temp.  If the
water temp already has the fans on, this switch still turns on, but of
course nothing happens.  Should the water temp fall below normal and the
temp sensor turns off, however, if the a/c pressure is high enough, the
relay stays on via the a/c pressure switch and the fans continue to cool
the a/c and water.  A second a/c limit switch is in series with the air
compressor clutch relay.  Thus, should the a/c condenser pressure rise
too high, this limit switch opens and thus the a/c compressor clutch is
de-energized, shutting down the compressor for safety.  Should any of
these switches not work, I'm sure they are still available.  I placed
one of mine from NAPA or such(don't remember for sure) when others were
working on my V-6 conversion which they completely screwed up.  I don't
have a wiring diagram of my diesel engine system, but I'm sure I've read
where some of the other guys in the group requested these and obtained
answers.

I suggest you contact Greg at S-Works and/or John Ferguson.  They both
are quite knowledgeable and have been most helpful in these matters.

As an old refrigeration man working both ammonia and Freon systems which
were non-standard, thus no specific quantity of refrigerant established,
I learned how to charge a system based on its pressures and pipe
temperatures.  Shucks, when we'd charge the ammonia system after a leak
at our ice plant, we'd simply charge until the suction line would
develop white frost right up the the compressor cylinders.  These were
old York and Vilter 2-cylinder compressors from 9 X 9 to 12 X 12 bore
and strokes running from 200 to 600 rpm.  Tells you how old I am.  But
the refrigeration principals are the same.  You charge the systems until
the liquid storage at the outlet of the condenser is sufficiently full
to provide a solid liquid feed into the evaporator under average normal
conditions.  Slightly overcharged is actually better than being
undercharged.  Undercharged overheats the compressor, while being just
slightly overcharged actually helps cool the compressor.  But too much
overcharge can do damage to the valve system in the compressor.  A GOOD
refrigeration man should have no trouble making it be acceptably
charged.  I think it was originally charged with Freon-12 which is a
no-no now.  See if you can't get the necessary gasket and O-rings
changed to tolerate the new R-16 or whatever number is the new standard
refrigerant for auto a/c.

The a/c wiring diagram is for the overhead evaporator unit.  You get the
these fuses and relays by dropping the "cloth" panel in the ceiling part
just overhead of the driver and front passenger center ceiling area.