I am going to do an ac service to my 79 f3504x4. It needs a dryer and an expansion valve, the parts are coming and i have the r12 or the r134. Should I keep it r12 or convert and see how it works? If the 134 doesnt work I can put r12 in but the oil might be an issue. I have a license to purchase r12 so the freon isn't a problem. I have both freons on hand and the instruments for all of them but I also wondered if the oil needed drained (What will drain) and replaced and what oil I should use in the old compressor with 134 and oil for r12. I have two 2oz cans of r12 "525 lowvis" or something like that will this oil work in this system with new r12? Is it worth changing the oil? There are no leaks so I think the oil is still in there as is the freon but it is probably old. Thanks for now.

 

Keep R12. If you convert to 134 you will need to replace pretty much everything to do it right. As for everything else, I have no idea. I had a shop recharge mine with R12 and they checked oil and added dye to the system so if it leaks I know where it leaks from.

 

Use ester oil its compatible with r12 residues

 

Well I think Ill try the r12 charge and see how I like it with the 525 vis mineral oil