Originally Posted By: SteveSRT8
most 134a systems seem to like being underfilled a bit. Our trucks run very cold with far less than spec amounts of refrigerant.
Agreed completely, and IMO this is another reason that so many of today's accumulator systems with a small total charge really ride on a knife-edge. They go from slightly underfilled and performing GREAT, to just plain underfilled and hardly cooling at all with a very small loss of refrigerant. My Jeeps and the PT Cruiser are prime examples of this- the PT is now 7 years old and my wife said that the AC wasn't cooling well this spring. I gave it a check, and the pressures were just barely below spec... about 1/8 of a pound brought it right back to normal. When the 99 Jeep had a leaky evaporator it was the same way, but every couple of months rather than every 7 years
A new evaporator core fixed that, but also drained my wallet because of the total dash removal required to install it. I'm too old and lazy to do that shtuff myself anymore... I'll still remove an engine, but interior and under-dash work while standing on my head just makes me mad. ;-p
I've retrofitted my two old rides with R-134a (total conversion with hard-line, evaporator, and condensor flushing, new rubber hoses etc.- not a hack job "conversion in a can.") They both retained their large receiver/driers and took a very big charge, even at the conversion rate of 80% by weight R-134a relative to the specified R-12 charge. Both have been working great for years now, and I think that's because the receiver/drier system is so forgiving in terms of charge. I *know* that the '69 must leak some refrigerant because it has its original RV-2 compressor still in there (the '66 has a modern Sanden). At their best when new and using R-12 and mineral oil, those RV-2 compressors were slightly leaky beasts with 2 head gaskets, 2 valve plate gaskets, an oil pump access plate gasket on the back, carbon front shaft seal, front bearing housing O-ring, and oil pan gasket all available to slowly weep refrigerant. But it still cools great and I haven't put an ounce in it since I converted it in about 2004.