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1966 Olds Toronado A/C

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    Long thread THANKS CB-89! Another couple off the wall things already may have been said? This car was intentional to stage release of 1st FWD Eldorado in '67. All those would have "Climate Control" I think lowest interior temp request ~65F? Front and rear well mixed may have ducts to rear if so were on floor?

    152a should read about like R-12 shown in charts already posted. That's lower pressures and higher caloric value than R134a so I'm told.

    BTW - a 10oz duster can from Harbor Freight last visit said in English it was 152a! Yes would need a side tap now to use that myself for remaining R-12 cans don't know what to trust with hockey can taps had one blow up - damn it! I'll just waste a duster can found elsewhere (only 8oz)
    see if the side tap seals well was costly will do tiny cans of just oil probably illegal now?

    If they are again going to bring up flammability of 134a think hard it's up like at 450F or something. Cars use gasoline too within a foot of A/C parts so I give up, YOU CAN'T FIX STUPID OUT THERE!

    MetroWest, Boston


      There is a big difference between gasoline and propane. If you get a gasoline leak, most will stay in liquid form, while all of the propane will immediately be vapor. As we know, it increases in volume like 100x in the phase change from liquid to vapor. Liquid doesn't burn, it must be in vapor form to burn, liquid gasoline is always giving off some vapor, so a match held over a liquid pool will ignite the vapor, and the heat will release more vapor, but propane will be vapor from the get-go and all of it will go up at once.
      Yes, most cars carry a fair bit of gasoline, but in a form that is not flammable. It is why in tank electric fuel pumps are possible.
      A pound of gasoline in the cab vs a pound of propane, one will burn the other detonate. Gasoline is run outside of the cabin, and never inside.
      R134a isn't very flammable, R 1234yf and R152a are both slightly more flammable than R134a. R290 is far more flammable than any of the others.
      Last edited by Cornbinder89; 06-10-2022, 05:29 PM.


        This was all a done deal with R-12 if not the power grab by Dupont to make $ if duped (easily I hear) never proven to harm a thing, didn't leak easily could use heavy parts to transfer heat so good to be true let's outlaw it? Not flammable by anything realistic. Move on this full blown antique now is cool IMO worth what it takes.

        Carry on I expect to hear this will be all done and if not also a perfect body or other issues made into a fine car,
        MetroWest, Boston



          I don't understand is why the POA set point with compressed air matters. I was under the impression that it was a way to approximate what the low end pressure was going to be once the system was operational. Air has different physical properties than a proper refrigerant, and the flow rates and pressures being pumped into the POA valve are going to be different too, never mind that my bench test takes place at room temperature, whereas a working POA runs much cooler, which will affect the density of the refrigerant and the viscosity of the oil that is suspended. To me this is a very dissimilar comparison.

          If my theory has some validity, I would be tempted to lower the POA setting a bit and try to get closer to 23PSI in the low side while the system is operational... And see what happens.

          I think it's clear that condenser performance has a big effect in my case, as vehicle speed has a noticeable influence on vent temperature. I was able to force more air from the mechanical fan to go through the condenser and that greatly improved vent temperatures while at a stop, but it's still coldest when the vehicle is moving at a high speed. How much extra efficiency can one expect from a modern parallel condenser vs a 55 year old tube and fin one?

          I am doggedly trying to avoid using R12 (which has become cheaper than it was 15 years ago), wanting to find a working solution with something that is readily available and hopefully will be made for many years.

          As to why R152A was never used widely as a refrigerant, I'm not sure. There is some flammability (and since cars already have plenty of flammable fluids and solids, I'm not particularly concerned about this), but it wouldn't surprise me that a large mega-corporation pulled some regulatory strings in DC to make sure that their product became the preferred refrigerant. Surely these kinds of things have never happened before.



            Originally posted by Tom Greenleaf View Post
            Long thread THANKS CB-89! Another couple off the wall things already may have been said? This car was intentional to stage release of 1st FWD Eldorado in '67. All those would have "Climate Control" I think lowest interior temp request ~65F? Front and rear well mixed may have ducts to rear if so were on floor?
            Yes, the Toronado and Eldorado of that era came with an automated HVAC system, called the Confortron. Mine is not entirely operational. I use a mechanical vacuum regulator to control the Power Servo, which is the brain (or actually the executive branch) of the system and gives me full heat to full A/C, with anything in between (including controlling doors and fan speeds), given a variable vacuum signal. Quite an ingenious system.


              IDK why 152a wasn't on the scene long ago? On vacuum source? Make sure you have or get one a check valve and vacuum storage tank as engine vacuum varies up to zero flooring it nothing would work.

              I still have a few parts to that 68 (call it a 98) vacuum switches (Trico?) for door locks whole chrome armrest thing the switches can swap. Long ago it wasn't that old I junked it YOUNG day 1 with it was dark and Winter a windy -10F engine froze but ran had unknown damage totally gave up early or would still have it!

              Not funny I got it from a mechanic he said he just checked antifreeze - apparently just water in it! Bummer big time!
              MetroWest, Boston


                The POA is a pressure regulator. It keeps the evaporator pressure (and therefore temp) from dipping below the frost point. It doesn't meter refrigerant, that is the Tx's job. It is there only to keep the minimum pressure in the evaporator.
                With this type control, the compressor runs continuously when A/C is called for but the evaporator pressure never drops below that at which it would frost over.
                Mopar product used a similar valve in the 60's and 70 called the EPR and Ford used both the GM POA and STV for the same effect. Once CAFE fuel economy became king, they switched to frost switches, which turned off the compressor when the evaporator temp dropped to the frost point, saveing a little gas, and being much harder on compressor clutches.
                Running the compressor all the time has some good points, the refrigerant is all stored in liquid form in the receiver when not needed and is available instantly, the low side is also kept at low pressure should the control need to handle more refrigerant. With a frost switch, the compressor is "off" when tripped, the low side pressure rises and the high side falls, then when more cooling is required, the compressor has to start under load ,pull the low side down and raise the high side to the condensing point.
                Since the valve is only a pressure regulator, the mass of the gas or its temp is immaterial to the set-point of the valve.
                For all the low side throttling valves, the set point is at or just very slightly below the pressure of the refrigerant at 32 deg F, this will keep the fins right above 32 deg F
                32 psi is 32 psi regardless if it is at -20 or +100 deg F
                If I had the choice, I'd use dry nitrogen for setting the valve rather than compressed air which will likely have moisture and oil in it.
                In Commercial refrigeration, a similar type valve is used on the outlet of an evaporator when more than one evaporator is used on one compressor and they are at differing temps, like refrigerator and freezer. It allows the low side to be low enough for zero deg in one evaporator and 32 or higher in another. By keeping the pressure up in the evaporator, it will not cool below the boiling point at that higher pressure.


                  Somewhere I read special automotive fitting were designed for R152a around 2001 or 2003?? about the time they were also evaluating R1234yf. Both these refrigerants required changes to the classifications used. It used to be non-flammables were class A and all others B, Now they have changed that to A1 and then A2 for "slightly flammable (R1234yf and R152a) and B R290 and stuff like ammonia
                  Class B refrigerants can not be used in inhabited spaces without very strict limits on quantity of refrigerant used.
                  I do not know why R152a lost out to R1234yf but it seams to have.


                    IDK for sure. Follow the bucks - Dupont is/was HUGE probably would like to be a Monopoly? Rubber products, refrigerants and chemicals of all sorts brand named them.

                    Chances are 152a is so easy to make it's scaring the greedy so change the rules, make impossible fittings to tamper with all for a buck? Bet you!
                    MetroWest, Boston


                      Originally posted by Mikel View Post
                      I am doggedly trying to avoid using R12 (which has become cheaper than it was 15 years ago)
                      Not overly surprised that R-12 price should be going down, the worldwide demand for it is dwindling as old vehicles and refrigerators go out of use. But folks who bought R-12 when high most likely don't like to face their loss....


                        It is hard to keep things in prospective. By early 1990's everything automotive had switched to R134a, that was 30 years ago. 30 years before that was when cars just started being common with A/C. Yes, I know they were around before that, but it wasn't every car like it is today.
                        Both R12 and R134a have had about the same run in automotive applications. We only notice it more today because we are keeping vehicles longer than in the 60's and 70's.
                        In stationary HVAC refrigerants are changing ever faster. I can't keep up with all the new refrigerants and mixes that are being used today, and a year or two down the road there will be different ones.
                        The Chlorofluorocarbons were all about ozone depletion, The HFC's are about global warming potential (GWP), who knows what the next problem will be.


                          Good afternoon,
                          Out of curiosity, typically how much more efficiency does a modern parallel condenser offer over a similarly sized fin and tube?


                            Good question? IDK is the answer but a guess is 25% but also can be lighter by about that. TMK 134a is about 80% the possible value of R-12 so increasing efficiency by that makes sense. The down side is they are not fixable, flushable yet ones swapped over worked fine in fact at the time had no choice it came with a note to reduce system capacity by 10 oz was about 25% of what that vehicle held in total,
                            MetroWest, Boston


                              That is something that is almost imposable to answer. In order to compare like to like you need to know many things, fin area and total volume of tube as well as surface area exposed to refrigerant. A comparison of mere physical outside dimensions doesn't come close to comparing the other things I mentioned.
                              In the 80's you could have two tube and fin units with the same outside dimensions and still have two differing capacities. Large trucks had large radiator area that could fit large condensers, but because they didn't want to impede the air flow to the radiator, they used units with a low fin count per inch. A similar sized unit with a high fin count would remove more heat from the refrigerant.
                              Tube and fin have a low surface area to volume ratio, meaning the amount of refrigerant in direct contact to the tube wall is small compared to the total volume of refrigerant in the tube.
                              Small thin oval or rectangular tubes have a high surface area to volume ratio. They also have a higher restriction because of this. To overcome the restriction many tubes are used in parallel. They are still a multi pass condenser.
                              In between these two types is the serpentine tube type, which also used a flattened tube with multiple passages.
                              The modern multi pass parallel flow has the most surface area to volume of any design and when combined with a high fin count per inch can provide more heat removal per unit volume of a similar condenser size of different construction and fin count. There are just too many variables to go on outside dimensions alone.
                              Another advantage the parallel flow has, is: Heat is remove fastest when the temp difference between the cooled and cooling medium are the greatest. So the vast majority of heat is removed near the inlet of the condenser and diminishing amounts toward the outlet. By have multiple paths near the inlet, it allows for more heat to be removed early, over a single tube design. This allows the rest of the condenser to have more area to remove the rest of the heat in the refrigerant, so by the outlet the temp is reduced more than with other designs.
                              It is almost impossible to compare apples to apples in this case.


                                Thank you both.

                                A/C is working well enough, but when the car is moving at a high speed it is noticeably cooler, so I hope increasing condenser capacity will make that cooling performance independent of vehicle speed. Unfortunately the core support blocks the mounting of pusher fans in front of the condenser and I don't want to start cutting the car.

                                Maybe a project for this winter.
                                Last edited by Mikel; 07-08-2022, 04:28 PM.


                                  Look into what can be done to seal the condenser to the radiator so the engine fan has to pull air through the condenser not around it. Cooler with ram air indicates an airflow problem.
                                  A larger condenser can help also. excess capacity that is not needed will just store liquid refrigerant and not cause any problem. Anything to get the liquid as close to ambient as possible, wil not be a wasted effort.


                                    Long thread - all fine it's what we're about. Seal it as close to air MUST go thru I doubt you need to add pusher fans? Do think that the same air has to exit generally down and out is also for the engine's heat.

                                    Shouldn't be a need to alter anything or mess up a total antique car in fact don't IMO. Stronger existing fan via clutch - right? Ha - once used to be able to get more with those by brand or just check out there what would just bolt up like for a truck or van but wouldn't be and Olds for trucks/vans of that time no harm in looking.

                                    What you get for parts must match IDK for sure nor what's available once an option called "Dessert Cooling" was a thing no chance to know that for this car??

                                    4 row radiators and some things noticed ONCE saw that a 60's Mustang I think ages ago now doesn't mean many others didn't offer that.

                                    IDK a van I had to drive plain Chevy had such a strong fan clutch took power away from engine was OE for the thing.

                                    Just Google around see if there is such a thing beware I don't always believe it by ads out there.

                                    If you don't have a 5 bladed fan I'm pretty sure you can fit one lots newer are for fan clutch vehicles (GM) was 4 if you didn't buy A/C for this when new no slippage was direct drive to belt speed whether needed or not, cold out or not special request for no A/C at all knew a few of those cars,
                                    MetroWest, Boston


                                      I did. In these cars the condenser sits about 1" ahead of the radiator (which has the mechanical fan and shroud behind it), with open sides and top, so that the air sucked by the mechanical fan bypasses the condenser. I got some high temperature foam strips and sealed those gaps, which made for a significant improvement when the vehicle is at a stop. I will keep fiddling with it.

                                      I do have a heavy duty fan clutch. Radiator is a recored 3-core. Interestingly, I think the foam I added is helping with cooling. With the open sides and top, ram air would flow through the gaps between the condenser and radiator, whereas when those gaps are closed, the air forced through the condenser has only one path to follow now, the radiator.

                                      The main problem at this point is not in raw cooling power but in the dash vents. There is a large central vent that cannot be adjusted side to side, and two smaller ones, one on either extreme of the dashboard. The one on the driver's side is blocked by the steering wheel, so getting air to one's face is very problematic, which plays a big role in being comfortable in a hot car.

                                      In 1970 Oldsmobile put a second vent where the clock is, which would give an unobstructed shot to the driver's face/chest. Next year I might do some surgery and retrofit such a vent to mine.
                                      Last edited by Mikel; 07-08-2022, 07:33 PM.