I have converted my 65 Sedan de Ville A/C to 134a and am not happy with the performance with the original system on hot days.
Is it necessary to replace the original condensor to a parallel flow typ? Where can I get one that fits?
I would also like to change to a sanden style compressor.
Does my Cadillac have a A/C superheat switch or an A/C pressure switch?
Any experience or help highly appreciated.
Quote from: DirkB on January 11, 2022, 06:34:08 AM
I have converted my 65 Sedan de Ville A/C to 134a and am not happy with the performance with the original system on hot days.
Is it necessary to replace the original condensor to a parallel flow typ? Where can I get one that fits?
I would also like to change to a sanden style compressor.
Does my Cadillac have a A/C superheat switch or an A/C pressure switch?
Any experience or help highly appreciated.
My 66 Fleetwood was also converted to 134. I don't know how they stood it in Scottsdale. I converted back to R12 last summer. Much better on a 95 degree day and evening.
Dirk,
Unfortunately you cannot legally revert back to the R-12 that your system was designed for. In-spite of a few success stories from typically folks living in very dry climates, switching to R-134a in cars using an un altered A-6 compressor results in complaints similar to yours. This subject has been discussed frequently in this forum because the results are typical. Without going into a long discussion I willl just answer your question by saying the problem is the A-6 compressor. With R-134a the operating compression ratio is substantially higher than with R-12, and as the compression ratio goes up the efficiency of the compressor goes down. In your case, something like 20%, resulting in ineffective cooling during periods of warm humid operation.
Going to something like a Sanden SD-7 will get you a compressor designed for R-134a but it's pump[ing capacity is 8.4 cubic inches vs. the 12.6 of the A-6. This leaves you short of capacity at full load again.
Four seasons Mfg. has a model 58098 that is designed for R-134a and is much closer to the A-6's capacity. There will be a bit of hose and mounting revisions, but I believe that would be the best choice to start. For your needs I would think the existing condenser should suffice since your cooling load is about 50% humidity.
No your existing system does not have a super heat or pressure switch in its circuitry. That came later.
Greg Surfas
https://www.hagerty.com/media/maintenance-and-tech/air-conditioning-dos-and-donts-refrigerants-and-the-law/
Scott
Dirk is in Germany
Greg Surfas
Scott and Greg,
Thanks for all the information. Yes I live in Germany and all the legal stuff applies he's as well and also no R12 to be found anywhere including neighboring countries. So I am forced to use r134a.
Greg, is this also a compressor I can use? : Old Air Products
21-2201HP | Compressor | Pro6TEN | High Pressure Style | Single Groove
They claim drop in replacement for the A6 or would I have the same pumping capacity issue you mentioned?
Dirk
Dirk,
I believe that the Old Aire Products unit would be the equal or slightly better.
Greg Surfas
Greg,
checking the internet the four seasons looks a lot like the old air unit. Maybe they are the same?
https://www.rockauto.com/en/moreinfo.php?pk=2195620&jsn=3
https://www.oldairproducts.com/product/21-2201sh-compressor-pro6ten-super-heat-style-single-groove
Dirk
@Dirk: since you are in Germany: do not go to a automotive shop. 90% of cars in Germany were converted to R134a or still have it. Try to find a large special shop that does professional cooling systems in offices etc. They have the tools to work with R437a. This contains 60% R134a and other stuff which comes close to R12.
Dirk,
Regardless of what you do, when your system is empty be sure and flush all the components thoroughly with a dedicated refrigerant system flush to remove any lingering mineral oil or sludge that might have formed.
Greg Surfas
Greg,
understood. Thanks!
Dirk
For my 1963,
I changed every single AC component and used a 7-vane Denso HD compressor.
Old factory components and R134 dont mix. Low pressure versus high pressure. Especially for humid southern climates.
AC needs everything to work in harmony. People on the forum that just switched compressors and hoses to R134 must live in North Dakota or Alaska. Or they are fine with an 80 degree cabin. 35-40 deg at the vents is not acceptable. You need 25-32 deg.
Also, older cars dont have the modern insulation and better glass we have today.
I dont use aftermarket kits, they suck. We picked and chose individual components from different manufacturers.
Granted, this is a full restoration of the car. But getting anything close to the factory R12 system or even a modern system today requires forethought.
Here are the people we used. They do systems for military vehicles and RVs.