Non-barrier hoses not "the" problem.

[wwest]

No such thing as refrigerant leaks (strickly) due to "non-barrier" hoses.......

My '92 R/awd Ford Arrestor, front + rear A/C, was just in the shop being converted to R134a refrigerant. Normal charge has been ~$160, this time ~$200.00. Difference was due to having to replace leaking o-rings on the rear of the Sanden compressor, something having to do with the refrigerant OVER-pressure relief valve.

Say WHAT..??

According to the Ford factory manual if the refrigerant pressure rises to high then the valve opens to atmosphere to bleed off refrigerant, but then "resets", closes, to preserve the system integrity.

But with the A/C compressor clutch controlled by a binary pressure switch why would the system ever go over-pressure?

The answer would be an inadvertently overheated engine, cooling system, radiator, heating up the nearby A/C condensor and thereby raising the internal liquid refrigerant pressure.

While I am by no means stating this as a definite answer for the reason our air-cooled Porsche's consistently lose refrigerant, it most certainly has a ring of truth to it.

Drive our Porsche's HARD on a HOT day, making full use of the A/C, and now shut down the engine. How high would the pressure go in the rear lid condensor, overall high side, with all that engine heat rising up through the rear lid condensor.

From what I could find on the INTERNET most automotive A/C compressors included an over-pressure relief valve, at least up until venting R12 to atmosphere was outlawed.

Could this be the real, actual reason, our refrigerant charge only last 2 years? The stage is certainly correctly set.

[JFP in PA]

Porsches do not leak refrigerant at any higher rate than any other make. Some cars are problem children and leak practically from day one; others go past 10 years with no leakage. In addition, as for “pop off valves”, they have been illegal on A/C systems for a long, long time.

We have a customer with a restored 1989 Cadillac that ran for more than 20 years on R12 and then burst one of the high-pressure A/C hoses. We replaced all of the hoses, converted the car over to R134A and it has run another 7 years without a problem. We also have a customer with a 2 year old Corvette that the dealer has never been able to fix the leakage on even after multiple trips to their shop. Sometimes certain cars are just a pain in the butt…….

As for what pressure either the high or low sides should be at, that depends upon the ambient air temperatures; Porsche, like most OEM’s publishes a chart that provides that data, but it is specific to the surrounding air temps.

[wvicary]

The Ford system used to open the high pressure valve at 500 PSI if I remember correctly. If your system has to be recharged every two years then find another garage to inspect the system and find the leak. Sometimes the are the devil to find but the freon is going somewhere at that rate.