A/C service is something that requires a high degree of precision. You drained, flushed the compressor of all mineral and added polyalkylene glycol a.k.a. PAG with out replacing the dryer? A recipe for failure for sure. If you left any mineral oil in the system it's worse. Poly
Ester oil is compatible with R12
and R134a and is much better suited to vintage retrofits. It is readily available in most auto part stores.
https://www.autozone.com/a-c-chargi...er-refrigerant-oil-with-ice-32-8oz/117707_0_0
Find a commercial AC tech who will most likely have nitrogen in his truck. Pressure test the system with nitrogen. Fix all the leaks. Evacuate properly and charge with approx. 80% of the original R-12 charge.
