R-134a conversion in an Auto A/C System
R-134a conversion in an Auto A/C System
(OP)
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





RE: R-134a conversion in an Auto A/C System
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.
RE: R-134a conversion in an Auto A/C System
Cheers
Greg Locock
RE: R-134a conversion in an Auto A/C System
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
RE: R-134a conversion in an Auto A/C System
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
RE: R-134a conversion in an Auto A/C System
Cheers
Greg Locock
RE: R-134a conversion in an Auto A/C System
Rod
RE: R-134a conversion in an Auto A/C System
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
RE: R-134a conversion in an Auto A/C System
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
RE: R-134a conversion in an Auto A/C System
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
RE: R-134a conversion in an Auto A/C System
Cheers
Greg Locock
RE: R-134a conversion in an Auto A/C System
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
RE: R-134a conversion in an Auto A/C System
All advise is appreciated.
captng1
RE: R-134a conversion in an Auto A/C System
h
http://www.imaca.org/sg-14.htm
htt
http://www.autofrost.com/
The autofrost site has a good discussion of the 12 to 134 changeover requirements.
rmw
RE: R-134a conversion in an Auto A/C System
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
RE: R-134a conversion in an Auto A/C System
BTW
Does "no hat,no play" still apply in OZ ?
RE: R-134a conversion in an Auto A/C System
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.
RE: R-134a conversion in an Auto A/C System
Thanks for the links!
captng1
RE: R-134a conversion in an Auto A/C System
This thread has not answered my question in regards to flushing the system? Is there a proper flushing solution to use and what is the process?
captng1
RE: R-134a conversion in an Auto A/C System
But, I would confirm that before you do it.
rmw
RE: R-134a conversion in an Auto A/C System
I'm restoring a 60's car with an add in system. It has about fifteen feet of hose running under the car to the trunk mounted evaporator. I want to replace these with tubing. What materials are acceptable for this. Obviously aluminum as this is offered for sale. How about Copper? Steel hydraulic line?
Thanx in advance, Steve
RE: R-134a conversion in an Auto A/C System
Back in the late 50's when I was working in a garage to pay my way through school, I did several AC installations (paint by the numbers) and helped in the repair of a couple Buicks and Cads that had the evaporator in the trunk. You might look up the particulars of these installations. Buick or Cad club, perhaps. The cars were around 55 models as I recall.
Rod
RE: R-134a conversion in an Auto A/C System
You have a unique installation. Do not compromise it by going CHEAP here. NO copper/NO steel/Stainless is better.
You can buy Stainless Steel flex tubing for a good price. Use riged aluminum (insulated) where necessary, switch to flex at those points. Seek manufactures as "Pacific Flex" or derivations of:
Come back here if no sites can be found.
Dollars are a few different, quality is enjoyment.
Be proud, buy the best type conduit system because you have done nothing more than that since you purchased that damn thing (car) inthe first place...
It's a thing of beauty to see somone rebuild a system like this using SST material. Yes it's a little more money but when you see someones eyes light up because they KNOW the extent of the effort. Stay the Course.
Wishing you Well
pennpoint