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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.
      Difluoroethane or R152a is an environmentally friendly, low greenhouse refrigerant, a substitute for R134a in industrial refrigeration systems.

      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.


                  • #10
                    Hello Folks, I realize this thread is a year old but I signed up to this website just to thank you and let you know that this thread on R152A conversion was a lot of help to me. I recently did this conversion to my '72 Buick and the POA pressure settings listed here were an integral part of that. I created a video on my experiment to help others in the future. Again, thank you for the info.


                    • #11
                      Thank you for the feedback, and glad we could be of help. I, for one am always interested in learning new things.
                      To be clear, when you set the POA valve you are setting the minimum pressure (temp) that the evaporator will get. It is like setting a frost switch, but instead of turning off the compressor and having to re start it under load, the POA hold the temp by holding the minimum pressure.
                      A frost switch measure the temp of the fins, so is set slightly above 32 deg F to prevent icing. Since the POA measure the temp of the refrigerant it can be slightly BELOW the freezing temp as the tubes and fins will be slightly warmer then the fluid passing through it.
                      If your drier has a sight glass, look and see if you are seeing all liquid, liquid mixed with bubbles or no liquid at all. You want to add enough to have all liquid at the receiver but not much more than that. This is assuming that the condenser has good air flow and heat transfer. You should be able to feel the temp on the condenser, hot at the inlet and evenly decreasing as you progress down, the outlet tube shouldn't be much if any warmer that the fins near the outlet. If the fins are cool but the tube warm, there is a poor thermal bond between the tubes and fins, and the condenser needs to be changed out.
                      Thanks for the video, I know the theory of different refrigerants but by no means have tied them all.
                      Last edited by Cornbinder89; 04-18-2021, 12:08 PM.


                      • #12
                        Thanks for that insight... I believe that 23 psi is likely going to be the sweet spot for the POA.. any less and you risk freezing the evap solid (I assume).... I’m sure humidity could also play a big role in that but I have yet to test it out. I shot for 23 psi in bench testing but ended up with 25 once it was on the car. With this I can achieve 37 degrees at the center vent with recirculating on and high fan speed. There’s no drier sight glass on my car which is fine since my drier is tucked out of sight anyway. This small amount of time and money has extended my cruising season to the entire year.

                        Thanks again


                        • #13
                          I would suggest writing down how much R 152a and what and how much oil on a sticker under the hood. Generic retrofit stickers available should have all the necessary blanks to fit in.
                          That way in a few years if you or someone else is making repairs, they don't have to guess and go through the trial and error you had to.
                          Nice video, by the way.
                          I just work on my own large trucks, so 134a and a bigger condenser works for me, but the classic car world might really benefit from something like you did, where lots of changes defeat the whole restoration.


                          • #14
                            Right now I have a small laminated label saying “20oz R152a” by the high side port so that it is out of direct view from the front but can easily be seen from the left side. I don’t ever plan to sell this car but if I do I will have to make it more apparent effort to avoid contaminating anybody’s recovery machine down the road.


                            • #15
                              Bogus919: Thanks for you checking it out also. Sorry again! Late reply I don't get notices?? I think said it's sold as "duster" like air in a can. A late tech was just side tapping cans of duster for R-12 OE vehicles ALL were CCOT set ups (clutch cycling oriface tube) types so can adjust LPCO (low pressure cut out) if frost seen alter those and done.

                              You don't really need the high side for more that adding some to a vacuum just see 1 lb pressure on low side know air isn't getting i in.

                              The subject was a fight I thought I read the demise of 134a, would become OE 152a so they gave it a name as a viable refrigerant.

                              If used OE I can't know where, there are about 295 world countries can make up their own minds what to do.

                              IMO it's not likely to harm it so I might try it if/when I run out of R-12 and still alive and care I could live without A/C (funny) for an A/C tech!
                              As far as stickers so you or another knows what to do - GREAT! I print on good paper for lack of higher tech ways, spray that with clear engine paint will last. Tape (high quality clear packaging type) that where it can be seen it tolerates cleaning, heat of engine AND can be removed if you or another wished to.

                              Good luck for success and no disasters but say so if that happens for another perhaps it could help :-)

                              MetroWest, Boston


                              • #16
                                I think the "powers that be" 1st made it a hard rule that auto A/C can't use flammable (class B) refrigerants. Then they wanted non ozone attacking, now they want non climate warming.
                                The problem is: those three requirements are mutually exclusive. Any two may be but all three no. They have now started backing away from the non flammable and saying low flammable is ok. That opens the door to things that were verboten only a few years ago. I think 134a is slightly less flammable than 152a, but both support combustion to some degree.
                                To get around their own rules they have made a new class of "slightly flammable" that can be used.
                                When the choice came to pick between 134a and 152a the difference in flammability and the fact both required different oil, 134a won that battle. It does seam like 152a would be better in retrofits, but I'm not sure. Certainly there is something to be said for "going with the crowd" in terms of availability.


                                • #17
                                  I know this is an older thread, but I came across this statement while looking up other stuff and it applies to this refrigerant:
                                  HFC-152a is an A2 flammable refrigerant as classified by ASHRAE 34 and should be used only with a secondary loop application. However, until MAC systems are developed to use HFC-152a (R-152a), no SAE Standards for system design, service equipment or service procedures have been established. The R-152a service fittings described within this Standard were established as part of the industry’s evaluation of replacement refrigerants and are maintained for future design guidance and to prevent potential refrigerant cross contamination


                                  • #18
                                    Sorry guys, I didn't realize there had been more replies. I didn't mean to be rude.

                                    I charged the system with R134A (by weight equivalent from R12) and it worked acceptably, although cooling really suffers when the car is at a stop (there is a large gap between radiator and condenser, with nothing to prevent air from the mechanical fan going around the condenser), so this lack of air flow through the condenser will need to be addressed.

                                    Ambient temperatures have dropped, so this will have to wait until next year, but I still haven't given up on R152A. After I address my airflow problem, I'll lower the POA setpoint to 23PSI and report back with my results.

                                    Thank you all who responded and my apologies for not following up.
                                    Last edited by Mikel; 09-16-2021, 08:52 PM.


                                    • #19
                                      When charging by weight, 134a should be 75%-80% of the R12 weight, so you may be a little overcharged. Also 134A also required a lower POA valve setting, around 26 psi IIRC.


                                      • #20
                                        Mikel - late myself as the site doesn't send a notice. By weight Cornbinder is right. Sorry if already said or asked but if this has a sight glass at least take a look but isn't considered reliable like when OE new. These held a pound too much no problem (some) as if expecting some leakage as normal.
                                        Don't forget there's always a good clue by "touch-feel" lines for temps in and out of evaporator, look for wet, not frosted return lines and that it makes condensate (water) if any humidity it's working about as well as it will IMO.

                                        Other: For acquiring 134a now check out the home centers for now outdated 12oz pierce only cans just seen here for under $6 vs double that. Give it up to loss if you use part of one doubt you can save partial use of one (either type of tap) lose it on me. Interdynamics (others) made brass taps with caps intended to save indefinitely help but no guarantee they'll work. LOOK FOR THOSE USED if you want to have plenty on hand ones I have, have "O" rings and wadding give you a chance anyway,
                                        MetroWest, Boston