I have an older vehicle that has AC, but it needs a recharge. It uses the older R12 refrigerant and it is very expensive and can be difficult to locate as it is not made in the US anymore. How do I convert it over to cheaper newer R134a? Can this be done without replacing the AC compressor?
Checkout the Auto AC board at AC Source
There are some good people on there.
Don's right. You do need to flush the old oil out of the system because they don't mix. Also it's difficult to flush the compressor so odds are it will not last if you don't replace it. The best thing to do is change the compressor out if its older at the same time, replacing all the o-rings too. R134 operates at higher pressures and it won't be as efficient, so you have to be careful not to overcharge. Older condensors designed for R12 might not cut it.
I have done it before. I just replaced all the seals and o-rings, cleaned out all of the old oil and then refilled with r-134a. That's about it. I did it on an '86 Volvo 740 and it worked really well.