ok
official charging method with a tank.
FULLY evacuated system. lines from charging manifold to car attached, and closed.
tank inverted for liquid dispersal, and valve open, tank resting on digital charging scale. preferably with an exact weight alarm, or a digitally controlled charging valve.
car and system OFF.
open the HIGH SIDE VALVE and add in 90% of indicated weight, close high side manifold valve, turn can back to gas discharge side up, then start the system. finish the charging with gas until the correct weight of refrigerant is indicated by the scale.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!