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1966 Olds Toronado A/C

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  • 1966 Olds Toronado A/C

    I've been working to revive the A/C in my '66 Toronado. I rebuilt the A6 compressor, had the hoses remade, replaced all o-rings, dryer, flushed the system, added 10 oz of PAG oil150 and 30oz of R152a (manual called for 4 lbs of R12, so 60% of that).

    I had tested the POA with compressed air and set it to 30 PSI. With the system running, it still read 30 PSI. High side was 80 PSI. The hose coming out of the evaporator was cool, but after the POA, it was very cold, to the point that frost was forming on it. Outlet air temperature was probably in the 50s (60deg day).

    Any suggestions?


  • #2
    I'm going to assume the "R152a" is a typo and you used 134A. If you can adjust the POA, I'd set it to 26 psi for 134a, that is just below freezing between 30 and 31 deg of refrigerant temp, that will keep the fins around 32 deg.or just a little higher.
    There isn't an exact conversion factor, but I would say 60% is on the low side, . Your high side pressure of 80 is low as well.
    A POA system hold the low side in the evaporator to a set pressure, the suction AFTER the evaporator can be much lower and that is why you see frosting.
    I'd set the POA and recharge with 75% of the called for R12 by weight, you may have to go higher up to 80%.
    How does the high side feel? How about the condenser? how warm is the outlet of the condenser?
    The temp that you are working at makes it hard to test the system under a good heat load. Anytime you are converting system, there will be some trial and error.


    • #3
      Ok, I did some web searching. and found R 152a, too new to be in my books, and I have no experience working with it. Although it is similar to R134a, it is slightly flammable (like R1234yf) .
      I don't know of anyone on this board who may be working with that refrigerant.
      I posted a link to info on it.
      If you are using this new refrigerant, I'm not sure we can help with the technical aspects. It did say it is similar to 134a but does have some differences. It makes the pressure/ temp chart useless and my guide on setting the POA may not be correct.
      Most of us are old auto A/C guys and don't see the new refrigerants. May be Nacho has run in to it?.


      • #4
        Welcome and you bring a host of new for here and first year of a configuration of that car! Added is NOW some strong info about 152a, cans of it sold and marked that way is in fact also a refrigerant. Problems are exacting it to a retrofit with discrepancies of what will work or not for an oil and how much if you still believe the original listed capacity of the system? New parts may have altered that.

        Can once again only be TMK that 152a is slightly more flammable than 134a but closer to heat exchange of the liquid gold standard of the R-12 it called for.

        If this car is in absolutely incredible condition brought back to as original as humanly possible I'd suggest the hunt for new R-12! I trust you already found how hard to impossible that is for you.

        So just from the lore of 152a I believe it was or still is next on the list to replace 134a. Not holding my breath for that but it is in use with some info about it your call if trust what you hear I have NOT used it to prove it for myself.

        So understood by me is you can use it but not with mineral oils, paraffin and I don't think PAG anything? It seems to work with Ester oil AYOR just know someone who does it routinely never witnessed.

        So with that he said chemically it's about 85% or better of the properties of R-12. So said it's larger molecule size does not have the propensity to leak like 134a battles with.

        Your call with sketchy info and documentation.

        IMO beliefs of the vintage at large and many model years newer than this is the factory fills new were overcharged by as much as 16oz and behaved and would also being low that much?

        IMO again this being the first will have a loooong interest in it for being so even original parts off of this would be quite useful and valuable indefinitely. So not just what I say just do take your time to make it as right as possible from any trusted sources. Best of luck with first time success at getting it going as intended,
        MetroWest, Boston


        • #5
          The POA keeps the evaporator pressure at a value that is just below freezing to prevent frosting of the evaporator. The difference in temp between the refrigerant boiling temp at that pressure and the fin temp is explained by the fact that no heat transfer takes place if there is no difference in temperature. Therefor you want to set the POA to a pressure that is just below freezing for that refrigerant.
          R152a claims better thermal efficiency, so have no way to guide you as to what pressures to expect to see, nor how much by weight to equal that of R12 in the system.
          1st thing I would do would be try and get the pressure of boiling at freezing and set the POA just below that point, then work by trial and error on amount of refrigerant in the system with a good heat load on it. That will mean waiting until temps are in the 90's (F) or better to get the amount right.
          I don't even know if R152a is compatible with the drier material used in the drier? .


          • #6
            The chemical composition is similar to R134a enough that I would guess it would be compatible with oils and driers that are used with 134a.
            Tom have you seen R152a? I have not and not being deep in the industry, had no knowledge of it, until I did a google search. Not sold to the general public and I haven't seen it at my refrigeration supplier in a display, not saying they don't have it. It was just flying under my radar!


            • #7
              Did some more digging and came up with a temp/pressure chart. Don't know who made it nor can I be sure it is correct.
              With that chart it looks like the POA should be set around 23 psi! At 30 psi the temp would be close to 40 deg, which could be why you having poor cooling.
              Attached Files


              • #8
                It's weird, I'm finding technical papers dating back to 2003 or so, there are even unique connector designs for R152a but it doesn't seam to ever have been adopted into auto use. I'm not really sure why it has been abandoned. While it seams it would be a logical upgrade/replacement for R134a, it doesn't look like it was ever pursued. I may be because it is still an HFC and falls under the regulation for that type of refrigerant.
                While safer than propane, it is still classified as flammable and that may be another reason for the car companies not developing it further.
                If you are going to continue down this road, I would take good notes and label the system with the amount and the refrigerant that is used, for anyone who might come after you.
                Other than the flammability issue it seams superior to R134a.
                In one design, I saw they used it to chill coolant, that was circulated in the heater core, so kept the R152a all within the engine compartment.


                • #9
                  I hope when you've had a chance to work with a bit you'll report back on what you found and what works and what didn't. I does seam like it is working to a point, but the POA setting is too high for the refrigerant used. I'd like to learn from what others have done as I have no experience on R152a and have found very little on it.