Join Date: Jan 2003
Location: Rapid City SD, Black Hills of South Dakota
That's a very important point that you're using ES-12, and not R-134 like I thought. I have used ES-12 before, very successfully in a 85 Jeep A/C. The good thing about it is that it's a function drop in for R12 (but regardless the EPA says it's not), is compatible with R-12 mineral oils and expansion valves, and works great generally. The bad point is that it will burn under a narrow air/fuel ratio range.
Also, ES-12, or any of the HC based refrigerants operate at a lower pressure than R-12, and certainly not 350-400 psi. It supposedly has 33% lower pressure than R-12. When I used it in my Jeep, I think I was getting high side pressures of 200-210 psi or so, with low side pressures of 30 psi, and great cooling.
I'm not familiar with the Alfetta A/C, but are you talking about a "Thermal" switch, or a "Pressure" switch? The pressure switch will be off a port usually attached to the drier, but not always. A thermal switch will be a temp probe in the evaporator to cut off the compressor when the temp switch senses a freeze-up of the evaporator.
In any case, do you know exactly how much oil is in the system? I did you drain the compressor and condenser and install a new receiver drier?? And no, the oil quantity (for example the 164 uses 4.8oz of oil total in the system) does not count towards the refrigerant capacity. And you are correct that it takes much less HC refrigerant than R-12. And as I recall (check the website to be sure) ES-12 is charged as a liquid (can upside down).
Too much oil in the system, even if a little over the specified amount, compromises cooling. Is it possible you have too much oil in the system?
How much refrigerant did you put in? Do you have the capacity specs for the Alfetta/GTV6 system?