Alan,
  Usually I don't respond unless I have a reasonable idea of the solution
to the problem.  I don't.  BUT that being said, if I were in your situation,
the first thing I would check is the fuses.  I know, this is a silly
suggestion, but the fact is there are five fuses connected with the A/C
system.  Especially in a situation like this where there is NO power to the
system it would be the first place I checked.  Not only the actual fuse but
the terminal box the fuse sits in as well.  These are notorious for having
bad solder connections  -- like most of the rest of the car.
   When I first got my XJ40 and I turned on the A/C it worked for a brief
time and then went out.  I found a fuse on the right side had blown that
controlled the clutch on the compressor as well as the blower.  Ironically,
it also controlled the thermostatically controlled fan on the radiator which
was shorting out everytime the radiator got hot enough to trip the switch.

       Just a thought!!

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