Air conditioning leak detector?
06-04-2006, 09:28 PM
#16
Sorry I was really tired when i wrote that... Funny thing is i responded to this yesterday, and recieved my EP609 certification card in the mail yesterday... anyway, Matt is correct the reason the system doesnt work very well on these car is because of the condensor design. The r-12 molecules are larger, so they have larger passages in the condensor, but the 134a is much smaller, so the 134a condensor passages are much smaller. When you put the much smaller 134a in the larger passages you cant get all the heat to transfer.
Freeze 12 is 80% 134a, and %20 142b...
the info i found on duracool is that it is known as HC-12 which means it is a flammable HC-hydrocarbon... from what i can tell it is not SNAP approved so therefor cant be used in the states, so be careful...
If you dont know, im me and i can tell you how to leak check your system when you place it in the vaccum once you have all your repairs done.
Mark
Freeze 12 is 80% 134a, and %20 142b...
the info i found on duracool is that it is known as HC-12 which means it is a flammable HC-hydrocarbon... from what i can tell it is not SNAP approved so therefor cant be used in the states, so be careful...
If you dont know, im me and i can tell you how to leak check your system when you place it in the vaccum once you have all your repairs done.
Mark
06-04-2006, 11:10 PM
#17
Race Car
Thread Starter
Nothing to be careful of. They don't check my A/C system at the border, and I live in Canada 
The molecule size isn't that different between R12 and R134A. The biggest difference is in their physical properties. R134A requires a much higher pressure differential, and also more cooling at the condensor. When in proper systems, the performance of the two refrigerants should be nearly identical.
However, we have R12 compressors and R12 condensors, so we should use R12 substitutes. That is why I am using Duracool.
If I bought a R134A compressor, and a proper condensor (i.e. the griffiths setup) I would be 100% confident that it would cool just as well as the original R12 system.
The molecule size isn't that different between R12 and R134A. The biggest difference is in their physical properties. R134A requires a much higher pressure differential, and also more cooling at the condensor. When in proper systems, the performance of the two refrigerants should be nearly identical.
However, we have R12 compressors and R12 condensors, so we should use R12 substitutes. That is why I am using Duracool.
If I bought a R134A compressor, and a proper condensor (i.e. the griffiths setup) I would be 100% confident that it would cool just as well as the original R12 system.
06-04-2006, 11:32 PM
#18
Not saying your wrong just trying to dispurse the information i have been taught.
There is no drop in replacement for r-12, as you have said it is required to replace certain items to have a 100% functioning system. That siad i have no experience with the dura cool, just have been warned of the fact it could be a fire hazard and is something I should never have to deal with here in the US.
About the Condensor, I have a crosssection of the different style condensors right here but dont have my digi cam.. r-12 uses a tube and fin style condensor while 134a uses a crossflow/parallell flow that is about 90% smaller passages. The only characteristic of the compressor that would stop you from using the orig compressor is if the front shaft seal is not serviceable, a seal compatable with the smaller molecules must be used or you will leak out the shaft seal along with all o-ring seals an actually all hoses. Barrier hoses should be used.
Disclaimer: This information is generic across all A/C systems I have no personal knowledge of the inner workings of the particular 944 systems, but all A/C systems are basically the same for what we are discussing.
There is no drop in replacement for r-12, as you have said it is required to replace certain items to have a 100% functioning system. That siad i have no experience with the dura cool, just have been warned of the fact it could be a fire hazard and is something I should never have to deal with here in the US.
About the Condensor, I have a crosssection of the different style condensors right here but dont have my digi cam.. r-12 uses a tube and fin style condensor while 134a uses a crossflow/parallell flow that is about 90% smaller passages. The only characteristic of the compressor that would stop you from using the orig compressor is if the front shaft seal is not serviceable, a seal compatable with the smaller molecules must be used or you will leak out the shaft seal along with all o-ring seals an actually all hoses. Barrier hoses should be used.
Disclaimer: This information is generic across all A/C systems I have no personal knowledge of the inner workings of the particular 944 systems, but all A/C systems are basically the same for what we are discussing.
06-05-2006, 08:44 AM
#19
Race Car
Thread Starter
Duracool won't ignite until a higher temperature than either R12 or R134A. Or at least that's what I have been told. It might be a hydrocarbon, but it has been tinkered with. I am not certain why it is not legal in the US, but I know it's not due to it being a fire hazard.
All of our hoses are barrier hoses, or so I was told.
As for the smaller molecules with R134A, I cannot be certain on that one without seeing the chemical formula for each refrigerant. I suspect that the physical size of the molecules has less to do with it than the pressures at which the different refrigerants operate..
The griffiths guy had an excellent explanation for the difference in condensor styles over on Pelican a while ago. I don't recall has exact explanation.
As for the compressor, hoses and O-rings thing... While I cannot say that R134A will or will not leak from O-rings where R12 did not, I suspect that all of the O-rings in a 20 year old A/C system are due for replacement regardless. I know that a different compressor should be used because R134A requires a much higher head pressure, and will push most R12 compressors beyond their limits.
All of this said, I never intended for this thread to become an argument about A/C system efficiency and such, simply for some advice on a leak detector, and once the leak is found, some advice on it's repair. I respect that there are many differences in materials and designs between R12 and R134A systems, and I will most likely use a R12 substitute in my system unless I find that one of the R12 specific parts is the culprit (i.e. compressor or condensor).
Although there are no exact R12 substitutes, I have found that duracool works very well. It results in a nearly instant cooling effect on the incoming air, and can bring the evaporator temperature down to freezing in rather short order. I suspect it works as well as/better than R12. Once the leaks are found, I would be more than willing to back this up with some hard data, whatever I can provide to either side.
All of our hoses are barrier hoses, or so I was told.
As for the smaller molecules with R134A, I cannot be certain on that one without seeing the chemical formula for each refrigerant. I suspect that the physical size of the molecules has less to do with it than the pressures at which the different refrigerants operate..
The griffiths guy had an excellent explanation for the difference in condensor styles over on Pelican a while ago. I don't recall has exact explanation.
As for the compressor, hoses and O-rings thing... While I cannot say that R134A will or will not leak from O-rings where R12 did not, I suspect that all of the O-rings in a 20 year old A/C system are due for replacement regardless. I know that a different compressor should be used because R134A requires a much higher head pressure, and will push most R12 compressors beyond their limits.
All of this said, I never intended for this thread to become an argument about A/C system efficiency and such, simply for some advice on a leak detector, and once the leak is found, some advice on it's repair. I respect that there are many differences in materials and designs between R12 and R134A systems, and I will most likely use a R12 substitute in my system unless I find that one of the R12 specific parts is the culprit (i.e. compressor or condensor).
Although there are no exact R12 substitutes, I have found that duracool works very well. It results in a nearly instant cooling effect on the incoming air, and can bring the evaporator temperature down to freezing in rather short order. I suspect it works as well as/better than R12. Once the leaks are found, I would be more than willing to back this up with some hard data, whatever I can provide to either side.
06-05-2006, 09:47 AM
#20
Racer
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My experience is that the compressor front seal is the most common culprit for leaks. ( after all of the fittings have ruled out) I think that the most reliable leak detection is the UV dye. Sniffers are very inconclusive. I use a a 12 replacement blend that I think works better than 34 and it doesn't care what oil is in the system.
06-05-2006, 03:09 PM
#21
Like i said before not arguing.. just like putting my new found knowledge to use 
from the EPA website:
"It has been illegal since July 13, 1995 to replace CFC-12 with the HC-12a® formulation that was submitted for SNAP review "
"May hydrocarbon refrigerants be used to replace CFC-12, commonly referred to as "Freon® ," in cars?
No. It is illegal to use hydrocarbon refrigerants like HC-12a® and DURACOOL 12a® as substitutes for CFC-12 in automobile or truck air conditioning under any circumstances. "
Your info about the ignition temp is correct 134 ignites at like 1500F, and duracool ignites at 1600F, but thats when it flashes, duracool will ignite at room temp and open flame, where 134a wont (if i understood that)
134A only requires 10% - 15% higher head pressure than r-12, but i didnt realize that duracool required such an undercharge, but now that i know its in fact a hydrocarbon it makes sence they cool well. The compressors in these systems can produce 400psi+
Directly from my text:
The refrigerent being used determines the hose to be used. Due to the molecular size differnce.
IT will be indicated on the line if ok to use 134a.
O-ring material will also be different for a 134a system.
from the EPA website:
"It has been illegal since July 13, 1995 to replace CFC-12 with the HC-12a® formulation that was submitted for SNAP review "
"May hydrocarbon refrigerants be used to replace CFC-12, commonly referred to as "Freon® ," in cars?
No. It is illegal to use hydrocarbon refrigerants like HC-12a® and DURACOOL 12a® as substitutes for CFC-12 in automobile or truck air conditioning under any circumstances. "
Your info about the ignition temp is correct 134 ignites at like 1500F, and duracool ignites at 1600F, but thats when it flashes, duracool will ignite at room temp and open flame, where 134a wont (if i understood that)
134A only requires 10% - 15% higher head pressure than r-12, but i didnt realize that duracool required such an undercharge, but now that i know its in fact a hydrocarbon it makes sence they cool well. The compressors in these systems can produce 400psi+
Directly from my text:
The refrigerent being used determines the hose to be used. Due to the molecular size differnce.
IT will be indicated on the line if ok to use 134a.
O-ring material will also be different for a 134a system.
06-05-2006, 09:16 PM
#22
Race Car
Thread Starter
It is illegal to use Duracool as a direct replacement. This is because of the fittings used. It make it possible to confuse duracool with R12, and if duracool is suctioned into a R12 recovery machine, it will contaminate both the machine and the refrigerant in the machine, making it very expensive to dispose of.
That is why when you read their instructions, it states that you must (perhaps by law?) change both the low and high side fittings to their 'special proprietary' fittings, which are in fact R134A fittings.
So technically Duracool is not a R12 substitute, it is an alternative refrigerant, and that is why the law is stated so funny.
I was under the impression that R134A required ~25-50% higher head pressures than R12. Perhaps I was misinformed.
O-ring material is pretty much generic now. They have O-rings that are R12, R22, R134A, hydrocarbon, etc. compatible, and most O-rings are made from this material. IMO if you have a 20 year old A/C system, it's time to change the O-rings, and I change all of the ones I can reach.
I can't say much about the molecular size difference without further reading, but barrier hoses have been around since the late 70's. The hoses on our cars are barrier hoses, and there is no concern there.
That is why when you read their instructions, it states that you must (perhaps by law?) change both the low and high side fittings to their 'special proprietary' fittings, which are in fact R134A fittings.
So technically Duracool is not a R12 substitute, it is an alternative refrigerant, and that is why the law is stated so funny.
I was under the impression that R134A required ~25-50% higher head pressures than R12. Perhaps I was misinformed.
O-ring material is pretty much generic now. They have O-rings that are R12, R22, R134A, hydrocarbon, etc. compatible, and most O-rings are made from this material. IMO if you have a 20 year old A/C system, it's time to change the O-rings, and I change all of the ones I can reach.
I can't say much about the molecular size difference without further reading, but barrier hoses have been around since the late 70's. The hoses on our cars are barrier hoses, and there is no concern there.
07-12-2006, 06:21 PM
#23
7th Gear
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I tried just adding Freeze 12 to my non-cooling a/c on my late '85 944 and at first it worked... for a few days or so. i just added it until i started getting cold air and didnt use any guage, etc... maybe a mistake. then it seemed like it wasnt cooling quite as well so i added more and almost right away i could literally hear the hiss of a leak. that was a couple years ago and i have been suffering in up to 105 degree heat since. i want to go back to r-12 and wonder if anyone can direct me to a step-by-step set of directions on how to first find and then fix all the leaks and tell me all of what ought to be changed... ie, what o-rings or hoses or what? i have a little air-compressor operated vacuum pump from Harbor Freight Tools... is that sufficient for vacuum? also, i just bought a new receiver/drier and expansion valve but not installed them yet... got them on ebay. thanks in advance... it's hotter than hell here.
