5-90 said:
I think he meant "converted from R-12."
The conversion to HCF-134a/R-124a is fairly simple - I've done a couple. You do need access to an A/C shop for two steps tho - having the system purged of R-12 (which is recycled,) and having a vacuum pulled on the system after you've put it back together.
Do not simply recharge with R-134a - the oils are incompatible, and you'll wreck your compressor in fairly short order...
If you decide to convert, you'll need to have the system "drawn down" to vacuum (to purge the R-12) and flushed (to get rid of the R-12 oil; ) then change the accumulator/receiver-dryer (that cannister under the compressor; ) then go back to the shop and have them flush out the system and draw it down to vacuum so you can charge it.
Flushing the system is mandatory - if you don't, you'll wreck your compressor in short order. Flushing the system will get the old oil freed up as well, and you do it before you change the accumulator/receiver-dryer, since there is desiccant in there that will soak up the R-12 oil anyhow (and you can't get rid of that.)
This would be a good time to check your compressor oil fill level as well - but that didn't change. Only the system oil (that gets mixed with the refrigerant) changed - and mixing the two makes them sort of "plastic" - they'll gunk up pretty much everything.
If your compressor is heading south on you anyhow, this would be a good time to change it - since R-134a runs a higher "head pressure" in the system, and a backyard conversion tends to result on a blown compressor head gasket. The Sanden SD505/SD507 has, I believe, R-134a type-rated versions available as well.
5-90,
But if it was converted to R-134-a, it would already be R-134a? In which case all he needs is R-134-a added and a leak test and leak fix done.
Where did you hear that R-12 had a different "system" oil from the "compressor" oil that needed to be flushed before switching to 134-a?
The R-12 oil is the same through out the entire A/C system and compressor. It is all mineral oil. Same stuff.
There are two different R-134-a oil types available. One of them is fully compatible with the old R-12 mineral oil (the other is not). I, and millions of others have run the R-134a with some of the old R-12 mineral oil (no flushing in other words) still in the system with no problems. The trick is figuring out how much of the new R-134-a oil to add which depends on how much of the old oil is still in the system.
If all the mineral oil is still in his system he does need to get most of it out, except for the oil in the compressor, but only to make room for the 134-a oil and liquified refrigerant in the condenser/receiver/drier. Then he needs to add less R-134a oil, just enough for everthing but the compressor. Compatibilty is not the problem (if he uses PAO oil, PAO = Poly Aline Glycol), too much oil in the entire system is the real problem.
What they do not tell everyone is that it probably takes at least a 50/50 mix of the two oils to get enough PAO oil in the system to get the remaining mineral oil to flow properly. The R-134a is soluble in the PAO oil but not the mineral oil (thus the initial problem) but the PAO oil is soluble in the Mineral oil (and visa versus). So if you add enough PAO oil and drain enough mineral oil to get a good 50/50 mix at the right volume, there is no problem.
Conventional wisdom is that 1/3 of the R-12 oil is in the compressor and another 1/3 is in the condensor just before the accumulator/dryer. So it probably makes more sense to flush and drain the condensor since the mineral oil left in it is just robbing the system of room for liquified R-134a and thus reducing the condensors capacity and requiring one to add too much PAO to reach the 50/50 blend, and thus ovefilling the system with oil.
I have not heard of blown compressors from too much oil (with in reason that is)! Sounds like an urban legand to me! I have heard of blown compressors from trash like decomposing hoses, poor condenser cooling resulting in excesive head presure, too much refrigerant causing too much head pressure, water vapor freezing and forming ice that blocked the expansion valve where open systems were not properly vacuum evacuated and the refrigerant got low.....
The problems I did have with my second conversion were that the compressor seal was old and worn on my old A/C compressor already and the R-134a is much harder to seal even in new systems. So I was loosing about 12 oz a month of R-134a towards the end of the second year. I finally got a good deal on a new R-134-a rated (had R-134-a seals) compressor and replaced it.
One real no-no is using the old R-12 A/C rubber hoses and connector o'ring seals with R-134a. The old hoses and o'ring seals at all the connections also need to be replaced with the new R-134-a compatable material. (I think it is Viton, not sure).
What 5-90 said out gunking up things is correct if you use the wrong R-134a oil. Do not use the Ester oil!!!!!!!
Ditto on changing the accumulator/receiver dryer, a must if he opens the system up and replaces the hoses (which I recommend).
Lastly, if you live in a temperate climate, like I do, 100% humidity, 120 F cool summer nights (LOL), the R-134-a does not cool quite as well as the R-12. It can cool as well if you increase the condenser and compressor capacity (which is rarely done). So you might consider staying with the R-12 if you live in the tropics.
And the R-12 ban was not a conspiracy guys! :laugh: It was just good business for Dupont whose patents had finally run out on R-12!