I am in the process of retrofitting the a/c in my wife's 92 Aerostar. I know that the charge for R-12 is 4 pounds and that the R-134a equivalent is 80-90% of this. What I can't find is the total charge or capacity of the oil is. I am replacing all the O-rings, the pressure switch, the accumulator/dryer and the orifice tube. Also studying to pass the 609 EPA certificate since the EPA is pushing to have R-134a regulated the same as R-12. No certificate - no 12 oz cans of R-134a!

 

I am not sure of the quantity of oil. When I replaced the r12 for r134a, I drilled a hole in the bottom of the old Accumulator to get an idea on the amount of oil trapped inside. I replaced that amount plus 7 ozs. Don't remember if it was Pag or Ester. No problems to date. Wife is very happy!
By the way, 4lbs of r12 w/auxillary unit, 3lbs of r12 w/no auxillary unit.
Good luck
reever

 

Thanks. The sticker on the a/c unit says 4 pounds of r12 but the vehicle has no aux heat/ac.