Mixing Freon
Freshman User
Joined: Apr 2004
Posts: 29
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To answer your questions:
1. Evacuating with a vacuum pump will not remove oil. The fittings are in the high point of the system.
2. The conversion kits come with the new oil.
3. The kits come with the fitting adaptors. Older GM's need a fitting not in the kit, but are sold next to the kits in the store.
1. Evacuating with a vacuum pump will not remove oil. The fittings are in the high point of the system.
2. The conversion kits come with the new oil.
3. The kits come with the fitting adaptors. Older GM's need a fitting not in the kit, but are sold next to the kits in the store.
Senior User
Joined: Apr 2004
Posts: 107
Likes: 0
I make a living doing commercial A/C work, hence my moniker. A couple of quick points:
1. R-134a is not a "drop-in" replacement for R-12. You will lose efficiency if you just do an evacuation, vacuum, and charge. I could give you the exact numbers, but off the top of my head it is something like 12%. In other words, you would need a 12% larger evaporator core to remove the same amount of BTU's, both sensible and latent, from an R-134a system than with an R-12 system.
2. The hoses in an old R-12 system will eventually fail if they are not changed out. This is due to two things- chemical incapatibilty,and the physical size of the refrigerant molecules. R-134a has smaller molecules than R-12, and it will seep into your old R-12 hoses eventually as they are not designed for this refigerant. Think of the old hoses as strainers, or filters. They held in the R-12, but they won't hold the R-134a forever.
3. Depending upon what style of expansion device is on the R-134a systems, your existing one may not work properly. Remember, this was all engineered by people who are much smarter than they are given credit for, and I tend to believe they knew what they were doing here.
4. Fittings, seals, and ALL of the old oil MUST be changed to do the job right. The hardest of the three is the oil. Commercial HVAC techs can buy a flushing solvent, but it's hard to use. If you don't get all of the oil out you run the risk of breakdown, wear, and early parts failure.
5. Lastly, new refrigerants come out almost weekly. If you do indeed know someone in the industry, ask them stop at their supplier to ask about the newer R-12 replacements. Many of them will perform MUCH better than R-134a in your truck.
After all is said and done, I would either sell the truck "as-is" with full disclosure, or pay to have it fixed properly ("properly" meaning fixing the leak and using R-12).
'Nuff said.
1. R-134a is not a "drop-in" replacement for R-12. You will lose efficiency if you just do an evacuation, vacuum, and charge. I could give you the exact numbers, but off the top of my head it is something like 12%. In other words, you would need a 12% larger evaporator core to remove the same amount of BTU's, both sensible and latent, from an R-134a system than with an R-12 system.
2. The hoses in an old R-12 system will eventually fail if they are not changed out. This is due to two things- chemical incapatibilty,and the physical size of the refrigerant molecules. R-134a has smaller molecules than R-12, and it will seep into your old R-12 hoses eventually as they are not designed for this refigerant. Think of the old hoses as strainers, or filters. They held in the R-12, but they won't hold the R-134a forever.
3. Depending upon what style of expansion device is on the R-134a systems, your existing one may not work properly. Remember, this was all engineered by people who are much smarter than they are given credit for, and I tend to believe they knew what they were doing here.
4. Fittings, seals, and ALL of the old oil MUST be changed to do the job right. The hardest of the three is the oil. Commercial HVAC techs can buy a flushing solvent, but it's hard to use. If you don't get all of the oil out you run the risk of breakdown, wear, and early parts failure.
5. Lastly, new refrigerants come out almost weekly. If you do indeed know someone in the industry, ask them stop at their supplier to ask about the newer R-12 replacements. Many of them will perform MUCH better than R-134a in your truck.
After all is said and done, I would either sell the truck "as-is" with full disclosure, or pay to have it fixed properly ("properly" meaning fixing the leak and using R-12).
'Nuff said.
Junior User
Joined: Jan 2003
Posts: 84
Likes: 0
Subcool is 100% correct!
Never and I mean never drop R134a in on top of R12! This would be comparable to saying you can mix ammonia gas with propane and not have any problems. While both have been used for refrigerants, they are two totally different chemical compounds.
R134a and R12 are not compatible. Probably the biggest incompatibility is in the oil compatibility. Where R12 systems use mineral oil, R134a must be used with an alkylbenzene oil. The two oils do not mix well. The alkylbenzene will actually breakdown the mineral oil. Also, R134a is not compatible with mineral oil and will not carry it through the system providing adequate lubrication to the parts of your system including (and most important) your compressor.
As Subcool mentioned, to do the job right you should replace all fittings and seals when you do this. Parts, especially rubber ones, that have been previously exposed to mineral oil will breakdown very rapidly when exposed to the alkylbenzene oil. Most important you must remove the old mineral oil from the compressor and flush the system. Remember, your drier or accumulator, whichever you prefer to call it, probably has a good amount of mineral oil in it too, and it needs to be replaced.
I believe Subcool covered the orifice (metering tube, expansion tube, whichever you prefer to call it) change as a must due to the different cooling capacities.
Hope this helps!
Never and I mean never drop R134a in on top of R12! This would be comparable to saying you can mix ammonia gas with propane and not have any problems. While both have been used for refrigerants, they are two totally different chemical compounds.
R134a and R12 are not compatible. Probably the biggest incompatibility is in the oil compatibility. Where R12 systems use mineral oil, R134a must be used with an alkylbenzene oil. The two oils do not mix well. The alkylbenzene will actually breakdown the mineral oil. Also, R134a is not compatible with mineral oil and will not carry it through the system providing adequate lubrication to the parts of your system including (and most important) your compressor.
As Subcool mentioned, to do the job right you should replace all fittings and seals when you do this. Parts, especially rubber ones, that have been previously exposed to mineral oil will breakdown very rapidly when exposed to the alkylbenzene oil. Most important you must remove the old mineral oil from the compressor and flush the system. Remember, your drier or accumulator, whichever you prefer to call it, probably has a good amount of mineral oil in it too, and it needs to be replaced.
I believe Subcool covered the orifice (metering tube, expansion tube, whichever you prefer to call it) change as a must due to the different cooling capacities.
Hope this helps!
