I have heard that when an automobile system is converted from R-12 to R-134a that the charge should be 'lighter'. Say approximately 80% of the capacity of the O.E.M. R-12. Does this mean the cooling capacity of the system is now diminshed by 20% ?? I know that systems which are designed from scratch to use the R-134a refrigerant will have copper instead of aluminum in the condenser/evaporator coils and this is because of the improved thermal conductivity. So when the R-12 is swapped out for R-134a you are already handicapped by the aluminum components. What about the less dense charge? Does the converted system have a chance of reaching the same cooling capability as the original? If not, what compromise is considered 'reasonable' ?? Thanks in advance for any help from all........ Bill93XJ
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R-134a conversion in an Auto A/C System 2
- Thread starter Bill93XJ
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Several "conversion kits" are on the market and are very efficient and cost effective. Strictly a DIY project for those of us with a bit of mechanical talent. So far I have converted my 91 Dodge/Cummins, BBC motorhome, BBDodge motorhome and, 90something Ford Ranger with 100% excellent results. The BBC/AC Delco system is as good or better than the R-12 and the Dodge takes a bit longer to cool but, once cool, is equivilent to the original R-12. No comparison with the BBDodge and the Ranger as the systems were down to start with. These DIY kits are possible by using PAG type lubricants that are compatible with the mineral oils of the R-12 systems. The oils are not my area of expertise (assuming I have ANY) and perhaps other members can expand on that aspect of the conversion.
The kits include instructions suitable for the novice but, I reccommend having the kits professionally installed if you lack the skills and confidence to do the conversion yourself. Just beware the shop that wants to charge you $1000 and up.
Rod
PS---Two of the above examples required a replacement 'dryer' (accumulator) and one need a new hose but, the other two had a simple R&R of the refrigerant.
The kits include instructions suitable for the novice but, I reccommend having the kits professionally installed if you lack the skills and confidence to do the conversion yourself. Just beware the shop that wants to charge you $1000 and up.
Rod
PS---Two of the above examples required a replacement 'dryer' (accumulator) and one need a new hose but, the other two had a simple R&R of the refrigerant.
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GregLocock
Automotive
I'd been told there might be problems with O rings when you swap over. Cheers
Greg Locock
Greg Locock
Before I sold my 37 Buick a couple years back, the Buick Bugle magazine published a DIY on converting 50's AC systems to R-134 and it did include an item on 'o' rings and dryers. It would appear that the latest conversion systems are using a lubricant that is compatible with the older material. Since the older systems are what I learned to install back in high school I can say that changing out the seals and o rings is no big deal anyway. I also read that the molocule sizes of the R-134a stuff were smaller than R-12 and would 'leach' out the hoses. So far this is just 'bunk'. The Dodge/Cummins is doing just fine five years later with no additional refrigerant added (knock wood)! Motorhome is fine after three years (I did put one new hose on it, though).
An aside---I don't personally believe that R-12 had as much to do with the ozone depleation you 'down unders' seem to be enjoying in the summer. Just my opinion, it comes under the heading of "excessive methane emissions" from dairy cows!
Rod
An aside---I don't personally believe that R-12 had as much to do with the ozone depleation you 'down unders' seem to be enjoying in the summer. Just my opinion, it comes under the heading of "excessive methane emissions" from dairy cows!
Rod
strokersix
Mechanical
Some items from a John Deere "A/C Retrofit Diagnostics and Service" manual for off-road machinery: R12 and R134 have similar pressures at 65F and below. Above 65F the R134 will have higher pressure than R12 up to 13% higher at 165F in a roughly linear progression. Recommended fill levels for R134 are 90% of the fill levels of R12 by mass. The manual states that cooling capacity of a minimum retrofit system will be reduced but it does not say by how much.
Minimum retrofit is defined as flush, new PAG oil, new receiver/drier, and R134 charge. Maximum retrofit includes all components except possibly the evaporator and condenser. Maximum retrofit maintains the best system performance and reliability. Automotive applications are more likely to get by with minimum retrofit due to less extreme operating environment and shorter life expected.
I personally have done the minimum retrofit on my '91 Suburban and it works just fine. There is quite a bit of practical information in the JD manual. If anyone has some specific questions I'll be happy to look for answers.
Mike
Minimum retrofit is defined as flush, new PAG oil, new receiver/drier, and R134 charge. Maximum retrofit includes all components except possibly the evaporator and condenser. Maximum retrofit maintains the best system performance and reliability. Automotive applications are more likely to get by with minimum retrofit due to less extreme operating environment and shorter life expected.
I personally have done the minimum retrofit on my '91 Suburban and it works just fine. There is quite a bit of practical information in the JD manual. If anyone has some specific questions I'll be happy to look for answers.
Mike
GregLocock
Automotive
Funny you should mention hydrocarbons. LPG is quite a good substitute for R12. Fortunately (for some shareholders) the industry managed to stamp it out as an alternative.
Cheers
Greg Locock
Cheers
Greg Locock
Greg, the vintage conversion article I was refering to also had a section on several R-12 replacements. I am not sure why one or more of them were not implemented---I suspect a cost analysis will give a good answer, though. At any rate, the time frame of the article (early 90's) would have been before the availability of mineral oil compatible PAG type oils. I don't know why the current refrigerant was chosen. I assume politics played a large part in the decision and somebody 'made money' on the deal. The newest conversion kits seem to get the job done for as little as $35. That makes the DIYer quite likely to tackle the job and may result in poor performance. Can't say as when these kits are professionally installed they appear 'bullet proof'. Castrol and many other 'big name' companies are jumping on this DIYer bandwagon, big time $$$$$$$! Obviously with the near non availibility of R-12 and the attendant astronomical cost we have no other choice if we wish to continue using our ACs.
Rod
Rod
One more item to toss in. Many countries allow the use of hydrocarbons (mostly a propane-butane mix) as a refrigerant, and it does indeed work well. In the US, the EPA does not allow the use of a combustible refrigerant where the compartment is occupied, ie: a house or auto. At one time, during the change over, one of the prominent news networks showed a rigged car, I think it was a mid 1980's Olds Cutlass, with a leaking evap core, and a spark was introduced into the pass compartment. Blew the windows out, all of them. If it were occupied, it would have resulted in an overpressure, leading to ruptured ear drums, eyes, and possible internal organ damage.
The EPA SNAP air conditioning guide shows which refrigerants have significant amounts of HC's. Anywhere one of these state "drop in" refrigerant, it does contain HC's. Pressures, triple point, and evaporator saturation can be very similar to R-12.
An associate of mine in Oz states that almost all autos down under do use HC's, but I am personally not aware.
Greg, any feedback?
Franz
The EPA SNAP air conditioning guide shows which refrigerants have significant amounts of HC's. Anywhere one of these state "drop in" refrigerant, it does contain HC's. Pressures, triple point, and evaporator saturation can be very similar to R-12.
An associate of mine in Oz states that almost all autos down under do use HC's, but I am personally not aware.
Greg, any feedback?
Franz
GregLocock
Automotive
I don't know where your associate gets his numbers from. I don't know of anyone, personally, who uses anything other than R12 or R134. However, I haven't tried getting a 12 year old car re-gassed, so it may be that this is reasonably common, but not talked about. I'd certainly consider it for my 18 year old heap, except that the AC still works fine.
The Cutlass demo was rigged of course, since the usual location of leaks is in the engine bay where the gas cannot accumulate to any significant extent. I can't remember ever finding a leak in the cabin, tho I've only had to find five leaks.
The motoring organisations here ran a nice little scare campaign on the dangers of LPG as a refrigerant, which may explain its lack of visibility.
Cheers
Greg Locock
The Cutlass demo was rigged of course, since the usual location of leaks is in the engine bay where the gas cannot accumulate to any significant extent. I can't remember ever finding a leak in the cabin, tho I've only had to find five leaks.
The motoring organisations here ran a nice little scare campaign on the dangers of LPG as a refrigerant, which may explain its lack of visibility.
Cheers
Greg Locock
Greg:
In the US, the General Motors / Harrison evaporator core has had a dismal history of evap leaks. Before I left the profession and got a "real job", I served as a master automotive technician for quite a few years, specializing in AC work, and made a very good seasonal living replacing evap cores. This was from 1969-1984. Visits to the AC school and by the Harrison GM rep claiming that there were "no more leaks on GM autos than the other two" were proved wrong by simple stastistical tracking. I averaged well over 100 Harrison units to 1 Ford, and over 250 units to 1 Chrysler. Now that said, Chrysler had their own problems with hose wicking, expansion blocks, flat flange sealing, and Ford with O-ring seals, but nothing like the Harrison evap cores. More than once, upon entering the cabin with my electronic sniffer, it would squeal just by cracking the door open, or by poking it in the AC condensate drain. Removing the core would show the entire bottom half dripping in refrigerant oil. No mistaking the diagnosis as a leaking hose!
My contact in Oz may have been referring to the re-gassing of older autos, but he was pretty insistant on it. Personally, I will take your comments as you would certainly have a better grasp on the OEM side.
Franz
In the US, the General Motors / Harrison evaporator core has had a dismal history of evap leaks. Before I left the profession and got a "real job", I served as a master automotive technician for quite a few years, specializing in AC work, and made a very good seasonal living replacing evap cores. This was from 1969-1984. Visits to the AC school and by the Harrison GM rep claiming that there were "no more leaks on GM autos than the other two" were proved wrong by simple stastistical tracking. I averaged well over 100 Harrison units to 1 Ford, and over 250 units to 1 Chrysler. Now that said, Chrysler had their own problems with hose wicking, expansion blocks, flat flange sealing, and Ford with O-ring seals, but nothing like the Harrison evap cores. More than once, upon entering the cabin with my electronic sniffer, it would squeal just by cracking the door open, or by poking it in the AC condensate drain. Removing the core would show the entire bottom half dripping in refrigerant oil. No mistaking the diagnosis as a leaking hose!
My contact in Oz may have been referring to the re-gassing of older autos, but he was pretty insistant on it. Personally, I will take your comments as you would certainly have a better grasp on the OEM side.
Franz
GregLocock
Automotive
Well you know who I work for, so you can guess where we had the leaks! I'm sure as an aftermarket refill LPG does get used, I just don't see a way of getting a handle on the statistics. Cheers
Greg Locock
Greg Locock
Bill93xj,
Your original question has peaked my interest regarding material selection. I'm quite curious who/what source stated that copper would be the material of choice in an r-134a designed system? I ask this because I work in the QC department of a Tier-1 supplier of heat transfer components. We build around 10,000 condensers and 10,000 evaporators per day and they are all 100% aluminum. An example would be a fairly new car, a Cadillac CTS, which I would expect was designed for r-134a. We build the parts, but no copper is used.
As for conversions...I converted my '85 Mustang to r-134a a few years back with a DIY kit from the 'Big-W' for about $35. I used guages to fill the system, and did use slightly lower pressures as Strokersix mentioned. It cools to my expectations and the outlet temp is about the same as the r-12. This was a 'less than minimum' conversion though...I just vacuumed it down, and added the new oil and 134a. The system has never been opened, but was low before the conversion. Tighening all the connections seems to be all it wanted.
IC
Your original question has peaked my interest regarding material selection. I'm quite curious who/what source stated that copper would be the material of choice in an r-134a designed system? I ask this because I work in the QC department of a Tier-1 supplier of heat transfer components. We build around 10,000 condensers and 10,000 evaporators per day and they are all 100% aluminum. An example would be a fairly new car, a Cadillac CTS, which I would expect was designed for r-134a. We build the parts, but no copper is used.
As for conversions...I converted my '85 Mustang to r-134a a few years back with a DIY kit from the 'Big-W' for about $35. I used guages to fill the system, and did use slightly lower pressures as Strokersix mentioned. It cools to my expectations and the outlet temp is about the same as the r-12. This was a 'less than minimum' conversion though...I just vacuumed it down, and added the new oil and 134a. The system has never been opened, but was low before the conversion. Tighening all the connections seems to be all it wanted.
IC
I need a professional opinion on changing an r-12 system to 134a. I have heard several different opinions and dont know what to believe? I have been told that the oils are different in the 2 gasses and when put together they are corrosive and will trash your system. I was told that the system must be flushed first. Other people have told me that there is really no propper flushing agent available on the market? I want to convert the system myself but need to know how to do it PROPERLY? Will a vacuum pump remove all the old oil from the compressor? I also have been told all O rings must be replaced in the system and also the drier?
All advise is appreciated.
captng1
All advise is appreciated.
captng1
Try these:
The autofrost site has a good discussion of the 12 to 134 changeover requirements.
rmw
The autofrost site has a good discussion of the 12 to 134 changeover requirements.
rmw
This is a pretty old thread, but the information it contains is still applicable. I would suggest that before you post your question again, you go to the beginning of the thread and read ALL the posts. Most, if not all, of your questions are already answered.
One thing that HAS changed...the cost of the refrigerant. Two years ago it was about $5 a pound and today it is more like $15!
Additionally---my Dodge needed one pound added this year after seven years and the motorhome is doing just fine.
Rod
One thing that HAS changed...the cost of the refrigerant. Two years ago it was about $5 a pound and today it is more like $15!
Additionally---my Dodge needed one pound added this year after seven years and the motorhome is doing just fine.
Rod
GregLocock
Automotive
You bet. Even in winter I wear 15+ sunblock and a hat when I'm sailing.
The Ozone Hole is getting smaller apparently, although I don't remember seeing anything about that for a couple of years.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
The Ozone Hole is getting smaller apparently, although I don't remember seeing anything about that for a couple of years.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
Somewhere either in the links I gave you or others that I saw when I googled "R-12 replacement refrigerants" I think I remember it saying that getting at least 50% of the oil out by changing the oil in the compressor and changing the dryer was all that was required nowdays.
But, I would confirm that before you do it.
rmw
But, I would confirm that before you do it.
rmw
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