Would anyone know if this has already been converted to r134a. I bought off a guy awhile ago and he said it would need recharged every summer but i doubt he was buying freon. It looks like an r134a fitting.
Looks like it to me, aftermarket screw on adapter. Besides, r134a gauges won't connect to r12 connections, and vis-versa.
Shoot some dye into the system to locate the leak. I wouldn't use any dye with stop leak in it.