Fox T-Bird/Cougar Forums  

BAAAAHHHHH......Just get an new compressor and parts to repair the system on the second and add R134 and oil. Run compressed air through the system to remove as much R12 oil as possible, but screw the R12 crowd. They obviously read too much, believe in President Obama, and do not like money. R12 may be as high as $200/lb now, you could blow your entire system up 4 times before reaching the costs of a complete R12 recharge. R134 refer is a derivative of R12 coolant and the oils are very similar. There will be very few problems as long as the systems are sealed. The oils main purpose is to lubricate the compressor anyway. The orifice tube will be a little large so the coolant will not cool as well as when it has constant air flow across the condenser at road speed. When I did this conversion in 1999 I noticed the difference in town as when on the highway and parts for conversion were, Ford only, costing way too much. You may be able to scavenge an orifice tube from a 5.0 1995 mustang in the JY as it will be R 134 compliant. I'm not sure if it will even work since the bracket systems are completely different. Look at em to verify.

R12 may be as high as $200/lb now, you could blow your entire system up 4 times before reaching the costs of a complete R12 recharge.

Unless you completely remove/flush all the old r12 oil, you cannot go with r134 period without destroying the new compressor. If the a/c systems are dry, you will have to replace the accumulator and possibly the orifice tube as they go bad also. If the old compressor went out, it likely contaminated the entire system and must be flushed either way. Backward flush the condenser, flush out the evaporator, and lines, replace the orifice and accumulator, and replace the compressor. Use the right amount of oil in the new system.

r12 is dropped in price lately and can be obtained relatively easily compared to a few years ago. Stick with the better performing r12 is my recommendation.

this is not true.  you can charge an R12 system with 134a withough flushing the system but you MUST use ESTER OIL when converting to 134a.  I do this all the time with no porblems at all.  do some reading on the A/C forums.  FYI I just converted my 79 cougar to 134a using this method and there are no problems and it blows ICE cold.

I may have incorrectly stated my earlier post and left some information out, yes. Using ester, you had better make sure you know exactly what is going into the system, along with alert anybody that ever touches your a/c system in the future. You don't just add oil into a system with some already in there and expect any good results, which I would want in Texas. The oil already in the system will be contaminated with chloride residue which causes acyl chloride when "mixed" with r134/PAG. The system may "work" and perhaps not "optimally" as JeremyB posted, but I would not recommend leaving any of the old oil in the system to anybody. You may be able to get by with ester if you MAKE SURE the r134 you are adding contains NO polyalkaline glycol in the canister but most small canisters in the parts store do to help restore "lost oil". All the ones at my local Autozone, Schucks, and Napa contain I think 0.5oz of one of the PAG's.

I would still stick with r12. The system was built for it and it's a more efficient refrigerant. Both refrigerants are illegal in the US to vent to the atmosphere and both can be purchased easily. Besides needing slightly more r12 in the system and costing a little more than r134, anyone would be much happier with how well r12 works over r134. r134 may also be replaced soon so once again, our cars would be behind the times if they have a 134 conversion done.

Agreed :) 

also to add.  the A/C forums recommend using ester oil when converting from an R12 system.