Just out of curiosity, I'm running 250lbs on the high side and 20lbs on the low side at 2500rpm on a 1988 300sel a/c system and I do not see any bubbles in the sight glass at all-even when the system starts up. Is that within specs? I misplaced my old a/c manual. Also, the system runs for 50-60 seconds then shuts down and will not cycle back on unless I shut the engine off. Any advise would be highly appreciated. Thanx Nick