Ok, when I got my 1990 volvo 240 I was told that the ac been fixed. When I quizzed what all had been done I got the responce, A new compressor and converted to 134a. Well last summer I noticed ac not putting out to well. I had checked by local shop they said just a little low on 134a but all was well. I tolerated it last yr. So here its spring time and Im getting 50 degree air when it 85 out. So Ive been reading and studying about ac systems. First thing I noticed on my volvo was the original dryer. So Ive ordered a dryer. I wanting to change back to R12. I understand pull a vacuum etc. What all should I do to get 134a junk out. I want to change it back cause I know it will never be great with 134a. I can get R12 which I should get a pretty good system if done properly. Thanks

 

Sounds like you are not sure whether you have r12 or 134 in there. First make sure, by the type of fitting you have on the low "fill" side. r12 and associated components have been out of use for a while now, since 1993 ALL US market cars use r134, so I have no idea where you can get parts... Surprised you have access to the r12 refrigerant itself, it is hard to get, it's expensive and you need a special license to handle and buy.

 

I know w.o. a doubt its 134a. I am wanting to change it back to r12. So what is the proper way to do that. I have the vacuum pump, guages and a new dryer. My car is a 1990 Volvo 240. My concern is the oil? Thanks

 

Theres no need to convert back to R12 to get a properly performing retrofitted system. You just need to monitor temperatures and pressures on the low side and add sufficient R134a as needed. A generic R134a pressure/temperature chart is sufficient. As there is already R134a, you don't necessarily need to evacuate the system. Be careful when adding oil if you choose to do so, to use ester oil, not PAG.

You'll want to find and fix any leaks using a UV leak tester.

You will also want to make sure your fan is functioning properly, as is your electric pusher fan. These can go a long way to a better performing system.

 

If you want to flush the oil, you can buy a/c flush solvents for that. Just google it, you can't miss. Getting the solvent out is no problem of course, the vacuum pump will get the rest of it. Add back white mineral oil. I guess you know that already. Leaving the old oil in would not really hurt anything. The reason people don't like 134A-style oil is that the ester reacts with water and you get acid from that. The acid would increase corrosion. Generally I don't see this as much of a problem in practice. It's important to have a good drier, and you are going to have that. But anyway, flush it out if you want. P.S. If I was getting 50 degree air, I would not touch it.

 

Its not R12 that I saw it was R12a which suppose to be compatible with R12. Thanks for the help.