compress ignite offers some wisdom here. I suggest that you pay close attention.

I am not jumping onto you because you bought the car in this condition, but this is a PERFECT example of one of the MANY problems that the junk refrigerants get you into.

If the system was originally designed for R12, use R12. If there is ABSOLUTELY NO WAY to use R12 due to Canadian law or some other crazy local tree huggers, convert to 134. Leave the junk refrigerants and their future problems for someone else.