The A/C on my 91 MV stopped working last year: it wouldn't come on. At
first I thought that the refrigerant was too low, so I had it charged.
Compressor still wouldn't kick in.

 I then replaced the two relays that are housed in the rear cabinet. No
change.

The Spanish VW dealer (where we live) won't work on it since this is a
U.S. spec vehicle and Spanish T2's didn't have A/C.  While on vacation
in Germany last year I took it to a VW dealer; they said that the entire
system would need to be replaced, without identifying a specific
problem.

An indepent shop here in Spain "hotwired" the system, so that when the
switch is turned on the A/C kicked in and worked �too well. It was
either on full cold (and would freeze up after an hour of so) or off. No
thermostatic control.

Has anyone had a similar experience?  I'm wondering whether the
capillary tube (sensor) in the overhead compartment might be bad, or the
thermostatic control (small black unit mounted vertically on the rear
pillar). Any ideas?