I have run into a problem and hope someone can suggest a solution. I know just enough to get in trouble otherwise.
I bought a 1996 Geo Tracker.Sanden SD7B10. It blew pretty cold air at idle sometimes but not at 30mph or above. Then a hose blew wide open. As briefly as possible-Hose replaced(low side at compressor), another leak fixed.Replaced schrader valves and o-rings for parts removed. Replaced dryer. I removed and emptied the compressor which had only a 1/4 oz of oil. There was a lot of oil under the hood though. Pulled vacuum. Added 90cc Pag oil specified to the compressor. Began to add 3lbs 2 oz of R134a as specified on badge under hood.

I was using a 30lb tank through a manifold with a scale under the tank. When 1 lb 6oz had gone in the compressor began to short cycle and the refrigerant stopped going in. The manifold showed 50 to 60 on the low side which dropped slightly when the clutch cycled off. The high side ran 400 to 450.

Just for future folks with the same problem I had misread the scale and had too much coolant in it. More than the 32oz it needed. The low side pressure should have read about 30 to 35 max.