The original Frigidaire A6 compressor is heavy but probably the best one ever made. One thing we often change on these old systems is the elimination of the POA valve. If it works good by all means keep it but if not they are very pricey anymore. Clean the condenser and evaporator coils, replace lines and filter/dryer, check the draw of the fan motor, clean intake air plenum under the windshield, and check all the ducts to the diffuser outlets. Put some PAG oil in along with 134A and it should cool fine.
