I would think the compressor came with 3 oz probably pag46. Although it should be blue pag 150. I allways go with the old school 6 oz for a compressor, so add 3, 2 for condenser, 2 for accumulator, 2 for evaporator. or, total of 9 oz for those older systems. We used to put a bit less 134 than R12, but the last ten or fifteen years, I've been filling them with the specified amount of 134 that is recommended for the R 12. In your case 3 lbs. Make sure you get a good vacume for at least an hour on the system before filling, or you'll have air and moisture issues later.
Good luck
Mac
Good luck
Mac
