- Location
- Rainy side of Washington
I would strongly recommend looking into an R152a conversion rather than R134a. Its pressures and refrigerant performance are more in line with R12 systems than R134a is, R134a typically needs a much larger condenser to perform as well. It's a well known conversion and I learned how to do it from an hvac nerd friend of mine.
Details...
When you convert you MUST flush all the old oil out (start by dumping it out of each component, then dump in some acetone, plug the ports, slosh it around a lot, dump it out, then flush with acetone) and put in the appropriate kind to use with the refrigerant you choose, whatever refrigerant it is. Each refrigerant is miscible with only certain kinds of oils just like oil and water will not mix.
R12 systems use mineral oil lubricant.
R134a systems use PAG (polyalkylene-glycol) oil. There are several different ones - PAG 46, 100, and 150. The numbers specify the viscosity measured in centistokes. Use the viscosity recommended by the compressor manufacturer for your model compressor.
R152a systems use POE (polyol ester) oil. I believe there are several viscosities of this as well.
None of these are particularly compatible with each other, except ester oil, which will mix reasonably well with any remaining PAG or mineral oil in the system and keep it from gumming things up.
(see http://www.underhoodservice.com/ac-compressor-oils-types-uses-differences/)
Next up... how much oil and refrigerant to put in?
I would recommend putting the same number of ounces of oil in as the system was originally designed to use. Just use the new type to match the new refrigerant.
For refrigerant it is a little more complicated. You want to use the same number of moles of refrigerant, not the same mass. A mole is a certain number (6.022x10^23 for those of you who are curious) of molecules. For any given chemical, there will be a defined "molar mass" which is the weight of that many molecules. So, you look at the sticker under the hood to determine how many kilograms or pounds* of refrigerant was originally specified, look up the molar mass of that refrigerant, divide weight by molar mass, then look up the molar mass of the new refrigerant and multiply by that. Now you have the number of pounds or kilograms of the new refrigerant to use.
* since you are going to find molar masses all in grams (all chemists use the metric system...) and you are dividing by a number of grams and then multiplying by another number of grams there's no real problem with whether you start with kilos or pounds, whatever you start with, you will end with. Use whatever you are most comfortable with.
Now, the best part? R152a is 1,1-difluoroethane. If you look at the cans of "canned air" on the shelf at harbor freight... guess what's in em? 1,1-difluoroethane. With a little bitterant added to keep people from huffing it. My wife's 1993 Buick Roadmaster currently has an AC system full of Harbor Freight canned air, and it works just as well as it did when it left the factory.
If you choose to run canned air in your system... I'm sure it'll be fine, no one has ever posted up about it causing an issue, but be warned, I am not a refrigerant expert (just a fairly well read amateur) and am not responsible for it if you do this and your AC system gets you divorced, makes your dog die, and drinks all the beer in your fridge. Make your own choice. It has worked quite well for me and everyone else I know who has done it.
Also, I have all the tools (vac pump, gauge set, UV light, can taps, etc etc) to do this... I'm not fixing leaks in your system, but if you buy the beer+refrigerant/canned air and are near central mass, bring your jeep with a flushed AC system and I'll fill it. Open offer.
Details...
When you convert you MUST flush all the old oil out (start by dumping it out of each component, then dump in some acetone, plug the ports, slosh it around a lot, dump it out, then flush with acetone) and put in the appropriate kind to use with the refrigerant you choose, whatever refrigerant it is. Each refrigerant is miscible with only certain kinds of oils just like oil and water will not mix.
R12 systems use mineral oil lubricant.
R134a systems use PAG (polyalkylene-glycol) oil. There are several different ones - PAG 46, 100, and 150. The numbers specify the viscosity measured in centistokes. Use the viscosity recommended by the compressor manufacturer for your model compressor.
R152a systems use POE (polyol ester) oil. I believe there are several viscosities of this as well.
None of these are particularly compatible with each other, except ester oil, which will mix reasonably well with any remaining PAG or mineral oil in the system and keep it from gumming things up.
(see http://www.underhoodservice.com/ac-compressor-oils-types-uses-differences/)
Next up... how much oil and refrigerant to put in?
I would recommend putting the same number of ounces of oil in as the system was originally designed to use. Just use the new type to match the new refrigerant.
For refrigerant it is a little more complicated. You want to use the same number of moles of refrigerant, not the same mass. A mole is a certain number (6.022x10^23 for those of you who are curious) of molecules. For any given chemical, there will be a defined "molar mass" which is the weight of that many molecules. So, you look at the sticker under the hood to determine how many kilograms or pounds* of refrigerant was originally specified, look up the molar mass of that refrigerant, divide weight by molar mass, then look up the molar mass of the new refrigerant and multiply by that. Now you have the number of pounds or kilograms of the new refrigerant to use.
* since you are going to find molar masses all in grams (all chemists use the metric system...) and you are dividing by a number of grams and then multiplying by another number of grams there's no real problem with whether you start with kilos or pounds, whatever you start with, you will end with. Use whatever you are most comfortable with.
Now, the best part? R152a is 1,1-difluoroethane. If you look at the cans of "canned air" on the shelf at harbor freight... guess what's in em? 1,1-difluoroethane. With a little bitterant added to keep people from huffing it. My wife's 1993 Buick Roadmaster currently has an AC system full of Harbor Freight canned air, and it works just as well as it did when it left the factory.
If you choose to run canned air in your system... I'm sure it'll be fine, no one has ever posted up about it causing an issue, but be warned, I am not a refrigerant expert (just a fairly well read amateur) and am not responsible for it if you do this and your AC system gets you divorced, makes your dog die, and drinks all the beer in your fridge. Make your own choice. It has worked quite well for me and everyone else I know who has done it.
Also, I have all the tools (vac pump, gauge set, UV light, can taps, etc etc) to do this... I'm not fixing leaks in your system, but if you buy the beer+refrigerant/canned air and are near central mass, bring your jeep with a flushed AC system and I'll fill it. Open offer.