Non-barrier A/C hose maybe not the problem?
 

I've been having a problem with the A/C (dual, front and rear[side]) in my '92 Ford Aerostar R/awd van. In reading up on the A/C description in the Ford factory manual I discovered something maybe important to Porsche owners. The compressor has a "fuse" to prevent high pressure damage, in the case of internal pressures being to high the "fuse" opens and vents the refrigerant to atmosphere until the pressure is within reason and then closes.

I have previously proposed that high refrigerant pressure "bypassing" the o-rings might be the reason we lose refrigernat on an annual or bi-annual basis. My thought was that with the evaporator full chilled to <34F the TXV valve would be fully closed while the high side has, might have, a "surplus" of liquid refrigerant. Now you shut the engine off and the HEAT rising from the engine cases the pressure to rise in the extreme in the rear lid condensor, high side overall.

Does anyone know if Porsche used such a compressor protection technique?