Posted: 7/7/2026 9:59:46 AM EDT
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Have an early 90s car that came with r12. Seller briught the car back from the dead and said he charged the AC and it worked but leaked down overnight. I did an engine swap without an ac compressor and plugged the AC lines. I’ve figure out a mounting solution for an oem r134 compressor and want to get the AC working. With the lines plugged at the compressor it holds vacuum so I’m about to install the r134 compressor and a new dryer. I don’t know what the previous owner charged the system with, but it had r134 adaptors installed when I got it. The car is the last year they came with r12 and the OEM info is ambiguous as to whether the orings are r134 compatible. The o rings are reddish brown, google says that means they are pure silicon and “not recommended” for r134 use. What oil and refrigerant should I use? Keep in mind I don’t know what’s was put into the system previously. I’d like to avoid changing the nearly 20 o-rings if possible. |
| You need the green o rings. And likely hoses too, as the 134 molecule is smaller than r12 and will permeate the rubber. New hoses have a plastic inner liner, "barrier hoses". Flush the system with a bunch of ac flush solvent and use the oil recommended for that compressor. BG Products sells an oil that claims to be ideal for conversion. New drier after flushing, i would flush each component while the lines are off for orings. I would replace condenser as well, geta parallel flow if possible. |
Dobro is watching you, and you dont even know it
when arfcom cares enough to let GD be searchable, ill care about dupes
when arfcom cares enough to let GD be searchable, ill care about dupes
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Originally Posted By somedudefromhouston: You need the green o rings. And likely hoses ..... Flush the system with a bunch of ac flush solvent and use the oil recommended for that compressor. ......i would flush each component while the lines are off for orings. I would replace condenser as well, geta parallel flow if possible. It looks like I could make an adaptor and simply pressure feed flush fluid through the system from the compressor connections in the engine bay? If I do the orings it would be trivial to clean each line separately..... Apparently toyota has the condenser available and it's on sale for $280. If the system is clean inside does it really need replacement? Or is it usually replaced because it has lots of nooks and crannys to hide debris or old/incompatible oil? Since everything is apparently r12 safe and leak-free, could I simply run a r12 replacement and r12 oil in the r134 compressor? Then I wouldn't need to worry about orings, flushing, etc? |
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Originally Posted By Morgan321: The compressor will require custom hoses so they'll be fine. I have r134 safe orings, but the sheer number (around 20) seems crazy. Engine is in the back so the lines run the length of the car and there are lots of joints. It looks like I could make an adaptor and simply pressure feed flush fluid through the system from the compressor connections in the engine bay? If I do the orings it would be trivial to clean each line separately..... Apparently toyota has the condenser available and it's on sale for $280. If the system is clean inside does it really need replacement? Or is it usually replaced because it has lots of nooks and crannys to hide debris or old/incompatible oil? Since everything is apparently r12 safe and leak-free, could I simply run a r12 replacement and r12 oil in the r134 compressor? Then I wouldn't need to worry about orings, flushing, etc? Is the condenser a coil type? You can see a single line with fins or is it like a radiator? You can easily clean the coil one with the single line. I did a Pontiac Fiero and it worked great. Changed the o rings, new compressor, office tube/screen and a new drier/ accumulator. I also flushed all the lines, condenser and evaporator. I found no metal anywhere so I was G2G. My original system had mineral oil for lubricant and when flushed out I went with a newer PAG? Oil with dye. Pag is not compatible with original mineral oil but Ester oil is. You can use either or atleast I could, but pag only with a complete flush. R134a is something like 80% total fill of r12. When refilling your oil after all the flushing distribute the total fill across the system. Some in the compressor before hokking it up, some in the drier, some in the condenser, etc to spread it out. If you don't have proof of buying the flush, drier, office, the 4 seasons compressor I bought voided the warranty. |
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Originally Posted By Jerret_S: Is the condenser a coil type? You can see a single line with fins or is it like a radiator? You can easily clean the coil one with the single line. My original system had mineral oil for lubricant and when flushed out I went with a newer PAG? Oil with dye. Pag is not compatible with original mineral oil but Ester oil is. You can use either or atleast I could, but pag only with a complete flush. If you don't have proof of buying the flush, drier, office, the 4 seasons compressor I bought voided the warranty. There's no debris or anything in the system, it's really just the unknown oil that is left and the question of whether it is compatible with whatever I put in. The original compressor didn't fail mechanically, it (or maybe the hoses) just developed a leak after the car sat unused for so many years. The oil that I can see is transparent and feels like mineral oil - is that what it is? The newer compressor that I figured out how to mount is for r134 and comes with PAG oil. Can I flush the compressor out and then use ester oil to eliminate the potential of having incompatible oil types? ETA: to clarify, flush out compressor, replace dryer, and use r134 with ester oil. No flushing the condenser or evaporator. I can blow air or nitrogen through the plumbing to eliminate most of the old oil. |