A/C from R12 to R124(?) in stages?

Stu Ritter, who fixed these things for decades had IMO the best take on this: "If you repace one broken pare another will fail and soon the labour cost adds up. If it's 10 yrs old, replace everything in one fell swoop and don't worry about A/C for another

Try some kind of leak sealer first.  R-134a molecule is smaller than R-12 so if it is leaking now, it won't be better using R-134a.  BTW, how often do you use A/C?  I remember while I was in upstate NY, the hot summer was like 2 weeks long :-) Guenter Scholz wrote: Hi all         in my '89 300E (pristine condition) my evaporator has a small (?we believe) hole. The re and re of the dashboard scares me not to mention the CDN

Once you convert, you cannot use another refrigerant without replacing all major components. To remove R12 a complete evacuation with correct equipment is required because of incompatability of R12 oil and the PAG oil used in

Your best way to go is to stay with the R-12 system. Find and fix the leak and/or parts that need to be replaced. R-12 is superior to R-134 in cooling. And the price of R-12 freon is dropping monthly. Repeat, stay with the R-12.