System was converted to 134a some 2 years ago by P.O.
Since then the DK compressor got noisy after one year, and the high side line began leaking. These were original parts. The compressor was changed out with a Seiko-Seiki from a 1993 940, along with the high side line. (An advantage is a high side port). After evacuating, filling the compressor per specs, and charging, all was normal.

This A/C problem started out early this summer with the air into the cabin gradually increasing in temperature. Figuring loss of charge, it was evacuated, leak tested (none) and charged. This time the temperature was 10 degrees higher than before, about 50 F instead of about 40 F. After several of these attempts, a complete tear-down was done starting about two weeks ago. Nothing amiss that I could see.

A variable orifice valve was installed, as was a new accumulator and most of the O-rings. All joints were checked for fit and seating.

The compressor is pumping, the condensor was blown out, as was the evaporator.

Current status: can't recharge, as 134a isn't drawn into the ACC, even with the pressostat leads for the ACC shorted and the compressor operating. The High and Low side pressures are the same @ 75 psi running, no cooling. The 2nd low side port, where the pressostat would be, has 0 psi. Used to be about 30 low and 150 high side.

My only remaining ideas are the three pressostats mounted on the condenser, but having no wiring diagrams, operating info, or pressures that should trigger them, I'm lost.

Anyone know the specs and functions? Or know where on the Net they can be found?
Anything!
Thanks very much (and we're still having 95-100 degrees F for the forseeable future).