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James McClure · 04-03-2010, 06:36 AM

Kalashnkov has it right, but I'll add this. The R134 molecule is smaller than the R12 molecule. With this in mind, the hoses are designed for R12 in our trucks and do not effectivly keep the R134 from leaking out right thru the hoses. If you have to replace the compressor, disassemble the system and replace ALL the "O" rings. Replace the reciever\dryer. Replace the expansion orface only if it's packed with a lot of silver looking material, otherwise it's ok. As stated earlier, the orface tube is directional. With all the lines off EVERYTHING, flush everything out with brake clean and then alcohol (they leave no residue behind to contaminate the system) Next, get the conversion hose set from GM or a reliable supplier to convert to R134 from R12. Flush out the compressor if it's used. Be me I would get a new one. System needs oil now. Depending on application this changes, so you will need the book. Usually, you drain the old one and then put 3 ounces (changes with application) more than the drain amount back in. Maker sure you get the right oil!! R134 & R12 oils are NOT compatable. They called the oil "pag oil" at GM. I don't know if aftermarket oil is called the same thing. Last thing, clean out the fins on the condensor and check between the radiator and condensor and get all the crap out of there. Shop vac and garden hose work. DON'T use a pressure washer or steam jenny. Even if you don't replace the condensor, system retrofits to R134 work pretty well. Hope this helps, Jim

04-03-2010, 06:36 AM	#11
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Factory A/C operational question Kalashnkov has it right, but I'll add this. The R134 molecule is smaller than the R12 molecule. With this in mind, the hoses are designed for R12 in our trucks and do not effectivly keep the R134 from leaking out right thru the hoses. If you have to replace the compressor, disassemble the system and replace ALL the "O" rings. Replace the reciever\dryer. Replace the expansion orface only if it's packed with a lot of silver looking material, otherwise it's ok. As stated earlier, the orface tube is directional. With all the lines off EVERYTHING, flush everything out with brake clean and then alcohol (they leave no residue behind to contaminate the system) Next, get the conversion hose set from GM or a reliable supplier to convert to R134 from R12. Flush out the compressor if it's used. Be me I would get a new one. System needs oil now. Depending on application this changes, so you will need the book. Usually, you drain the old one and then put 3 ounces (changes with application) more than the drain amount back in. Maker sure you get the right oil!! R134 & R12 oils are NOT compatable. They called the oil "pag oil" at GM. I don't know if aftermarket oil is called the same thing. Last thing, clean out the fins on the condensor and check between the radiator and condensor and get all the crap out of there. Shop vac and garden hose work. DON'T use a pressure washer or steam jenny. Even if you don't replace the condensor, system retrofits to R134 work pretty well. Hope this helps, Jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.