If it was converted from R12 you don't want to use the info from the factory installed plates.
A rule of thumb for R134a is high side pressure in psi should be around 2.2 to 2.4 times the ambient temperature in degrees F, i.e. the temperature of the air that your condenser has to cool with, of the area in which you are performing the charge.
A rule of thumb for R134a is high side pressure in psi should be around 2.2 to 2.4 times the ambient temperature in degrees F, i.e. the temperature of the air that your condenser has to cool with, of the area in which you are performing the charge.
