I've probably done 100 conversions to R134, in the 80's you had to replace everything but in the 90's they figured out just drain it put in some PAG oil and charge it with R134. That's it no big deal, and it works great.
I can look up how to drain it (if there is anything in it) and maybe try doing 134a, from most of the reading I did it's not any better than r12 just cheaper correct? Does it matter which viscosity PAG oil to get?
