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Hi, Jim
Sorry about the delayed response -- I was on a road trip away from my computer.
I was told that you need to be careful flushing out the oil from R-12 systems. It's fine to use a flush on the condenser, evaporator, and compressor. You should replace the receiver/filter/drier rather than flushing an old one, however. The main danger with flushing is with the hoses. More on that in a moment.
You can flush the compressor yourself by pouring the flush into it and manually turning the pump. The easiest way would be with the compressor off the car, though it's a hassle wrestling it off and on. If you leave it on the car, you'd disconnect the hoses (after having the R-12 removed, of course) partially block one port, and pour the flush into the compressor through the other port to fill it up. Then turn the pump by hand to work it through. It's apt to be messy as the flush spills from the ports, but it will all evaporate out eventually. If you do this, your compressor will have no oil in it, so you have to be careful when you put the system back together and ensure you get the proper amount of oil introduced with your R-134a charge.
Here is what I was told about hoses: the oil for R-12 gets into the rubber of the old hoses and seals them internally. If you use a flush through the hoses, you strip that sealant out, and the hose becomes porous (at the molecular level) to R-134a. If you use a flush product on the hoses, you'll end up having to replace the hoses or recharge the system every year or so as your refrigerant gradually escapes through them. Therefore it's best NOT to flush the hoses if you're keeping them. If you're going to flush the whole system including hoses, you might be better off replacing all of the hoses.
To answer your other question, the compressor(s) I got from Sobstory had stickers on the side which said they were compatible with both R-12 and R-134a systems. The oil inside was clear, unlike the oil in the R134a kit, or the R-12 oil, which was yellowish. My guess is that whatever the compressor comes shipped with is not the same as either the R-12 or the R-134a lubricant, but is something that is compatible with both of them. ??? I never thought about it too deeply. Maybe it is just an interim lubricant for shipping and it evaporates out when the system is vacuumed? I just presumed that since the sticker said it was compatible with R-134a, it was okay. I was putting in oil with the recharge kit anyway, so I know I've got adequate lubrication.
I've never heard of the emulsifiers, but I'd be skeptical about that. Everything I've read says the two types of oil are incompatible.
If you vacuum out your system and replace your filter/drier, you'll get most of the R-12 oil out. I didn't flush my system (though I did replace the compressor) so if there was R-12 oil left in the hoses, evaporator, and condenser, it's still in there. A refrigerant tech told me that the oil is mixed with the R-12 and when you vacuum freon out the system, you get 99% of the oil. I think he just made up that 99% number, but it makes sense that a lot of that oil would be removed with the freon, even if you didn't flush it.
Here's my thought on all this: the R-134a oil is made to mix with R-134a, and the R-12 oil isn't. So inside the system, after you've done the conversion, you probably have a film of R-12 oil coating the insides of your hoses and old A/C parts (like the condenser), providing you didn't use a flush to clean it. It won't mix with R-134a, so it probably pools and sticks wherever it happens to be.
You've also got the new R-134a fluid (liquid and gas) flowing through the high and low pressure sides of the cooling loop, and it's got the new R-134a compatible oil mixed in with it. The new oil is suspended in the R-134a, circulates with it, and is what is now providing continuous lubrication to your compressor pump instead of the old R-12 oil. I believe it is important to remove as much of the old R-12 oil as you reasonably can, if only to make space available for the new stuff and not have large quantities of the old stuff pooling inside the system. As far as I know, however, the old oil won't cause any damage to the system, though if there's a LOT of it in there, it might reduce cooling efficiency. You can't use ONLY the old oil, because it doesn't dissolve in R-134a, and thus won't be carried through the compressor to lubricate it. So you need the new type of oil that works with R-134a. Does that make sense?
Good luck with your conversion. Now that I've done it, I don't consider it a particularly brutal job. It takes some time, but each step of the process is relatively straightforward. I got a lot more frustrated fiddling with my rear speaker adapters than I did installing the compressor or other A/C components!
- = M = -
'87 900T 174K
posted by 208.63.213...
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