A/C-Conversion R12-R413a-R437a-R134a

Discussion in 'High Tech Retrofits' started by ManfredT, Jun 2, 2019.

  1. ManfredT

    ManfredT New Member

    Messages:
    2
    Likes Received:
    0
    Joined:
    Jun 2, 2019
    Hello all, at first, please excuse my very poor english !!!

    Since the early 90s I own a Camaro 1975, 350 ci, with factory A/C.

    At this time it was filled with R12. A few years later R413a was used (R12 no longer available in Europe), and years later R437a was filled, until now. The compressor (A6) is going leaky and I replaced it with a rebuild (A6). But the new one is filled with PAG150 compressor oil and therefore I "must" switch to R134a said the A/C Shop. After all was done, now the cooling is "weak !!!

    But I am doubt about the "filling amount" of R134a:

    Original R12 was 3lb. 12 oz. ( 1,700 kg in "european Units") as in the Camaro Drivers Handbook
    R413a and R437a amount filled at the shop was 1,600 kg ( About 94 percent of original)

    >>>>>>> And now R134a only 1,000 kg was filled !!! (nearly 60 percent ) <<<<<<<<<

    Why !?! What could be the reason for doing so ? Could it be cause the weak cooling ?

    Of course , I had to ask the People at the A/C Shop but I am very interested in the answers of the experts in the Forum.

    Thanks for your comments !
     
  2. ssupercoolss

    ssupercoolss Veteran Member

    Messages:
    685
    Likes Received:
    164
    Joined:
    Nov 3, 2015
    Location:
    PA
    Was the system flushed? you sure had a bunch of different refrigerants in there.
    If they were still using POA valves in '75, that really should be re calibrated for use with R134a.
    your R134a charge should be about 75% of R12 charge.
    A parallel flow condenser will work better than the stock tube and fin condenser. That item there will typically show a decent drop in temps.
    R134A wont cool as well in an R12 system. Usually the results are just "ok" without some other tweaks.
     
  3. ManfredT

    ManfredT New Member

    Messages:
    2
    Likes Received:
    0
    Joined:
    Jun 2, 2019
    No, the system was not flushed, but vacuumized for several hours at the shop.

    At the time of 1,0 kg charge of R134a we had some cold spring days (About 50 °F ambient temperature). They stoppt charging because the temp. of outflowing air at the vents was going down to 39 °F.

    But now we have hot summer days with about 85 °F outside. With the full amount of charge 1,6 kg the temp at the vents is 50 °F . That seems to be OK !

    I look for a new parallel flow condenser, as you suggested, for better efficiency.

    Many thanks !
     
  4. 70lt1z28

    70lt1z28 Veteran Member Gold Member

    Messages:
    3,016
    Likes Received:
    532
    Joined:
    Oct 3, 1999
    Location:
    Beavercreek, Ohio, USA
    Not sure how "forward looking" you are, but you may want to consider the change to R-1234yf. It will soon displace R-134a as the default refrigerant and R-134a will eventually be phased out, just as R-12 was.
     
  5. supwicha

    supwicha Veteran Member

    Messages:
    181
    Likes Received:
    13
    Joined:
    Feb 23, 2014
    Location:
    Victorville, CA
    A couple things, I have years of A/C experience: 1) R12 and R134 will not be charged ounce per ounce the same, so do not expect to charge per volume. The technician much charge the system based on pressures based on outside ambient temperatures. R134a properties are such that the pressures will be higher with a less volume of refrigerant, 60-70%% is pretty darn close to what I would expect. If your system was charged to the same volume as R12, you would probably hit 400-450 PSI on the high side and the relief valve in the compressor would vent. 2) The BIGGEST problem with any R12 to R134a conversion is the condenser. R12 condensers of yesterday are not very efficient, nor where they designed for R134a and the design is NOT the same. They are not able to dissipate heat as quickly as R134a needs, to work properly. The condenser must do as its name implies, it must take high pressure gas, cool and condense it to a high pressure liquid. If your system is not able to get high pressure LIQUID to the expansion tube and evaporator, you will have not have good cooling. A test is to run the engine at about 1,000-1,200 RPM with the AC running, and use a garden hose across the condenser. If you notice after a few minutes of operation that it is performing better or good, your biggest problem is going to be the condenser. Another problem is airflow requirements for the condenser. Not knowing what your setup is, you may notice that while the vehicle is moving at consistent speeds it may cool better, but quit working once you slow down. Again, the condenser cannot do its job properly. What I did on my particular car was I used a new R134a condenser from a '95 caprice which required a little modification. You would need to eliminate the orifice tube or POA that is at the evaporator inlet as the expansion tube in the caprice is in the condenser. It will NOT work if you remove it from the condenser and use the stock Camaro location (I tried this already). You will also have to modify two of your hoses to adapt to the new condenser. I will say this, mine cools beautifully with R134, but you need to do more than a compressor swap and refrigerant change. R134yf is NOT going to be a viable solution for you for many reasons. 1) Cost - 10lbs of this refrigerant can be as high as $800. It is a very high pressure system, not compatible with your compressor. Your hoses, fittings, and lines will not be able to contain it as the molecular construct of this refrigerant is so small, it will leak through rubber. These systems are "sealed" systems, almost like a refrigerator. Many of these systems actually have metal tubes enclosed and a secondary metal tube. One advantage is the amount of refrigerant in these systems are even less than R134a by far, but again this is just not going to be a practical solution for you. Not to mention, when you found out hundreds of dollars worth of refrigerant leaked out in a couple of days. Upgrade your condenser, and yous should have good results. Lastly, your system absolutely should have been flushed out. Even with vacuum applied, it would not extract the mineral oil that is in the system, as well as any contaminants from the old system. You also need to use "barrier" o-rings and hoses throughout the system. Hoses designed for R12 will hold R134a for a period of time but will leak past the rubber like the R1234yf because the molecules of the refrigerant are smaller than the rubber that was used to construct R12 hoses. If you look at my Camaro build thread, I have a section with photos of my R134a conversion.
     
    BillyDean7173 likes this.

Share This Page



  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.