What I heard about the R134A systems was to try and have the High Side not higher than 2.2 x Ambient, so 220 PSI at 100*F Ambient.
When I tried to charge our "Dealer Air" on a rig like Jose's up to Low 20's Low Side (with 134), the Compressor got balky. Clutch Hub would STOP! Either the Belt or the Clutch itself would slip and squeal. I hooked up the High Side gauge and it was in the upper 300's! All this on an old afermarket system with the old stainless worm-drive hose clamps! That was when I knew I had to back off the charge. Low side was running in the low teens before High dropped into the 200's. I still couldn't use "store brand" belts. Had to be NAPA, Dayco, Gates, etc.
But yes, it cooled. At a cost of at least 0.5 highway MPG, and when 8 (A/C Off) is a Personal Best, need to get the compressor efficiency up. That's why I suggest converting to an Axial Compressor.
