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R-134a vs R-12 Question

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  • R-134a vs R-12 Question

    My 1988 Oldsmobile Toronado Trofeo came from the factory with R-12. The previous owner changed it over to R-134a. This was done at an Olds dealer. The a/c blows nice and cold. The problem I’m having is I am getting a “Low Refrigerant” warning, and then a “Very Low Refrigerant” warning. I bought a can of R-134a with a gage on it, and when I hook it into the system the gage shows that the refrigerant is at the correct level. So my question is, when converting from R-12 to R-134a, is there a refrigerant sensor that needs to be changed?

  • #2
    Those cans with gauges can't be trusted. That color chart bull is just that A/C pressures are a pretty complex algorithm taking in all temperatures, engine RPM then see what pressures are. Pressures do not tell of how much product/gas is in the system - know that.

    The best way is (need a shop the equipment would be so costly no worth it) ask to just evacuate and charge. Tech would look for stickers of the retrofit what amount worked right.

    About 80% if condenser is original or specs of original '88 was 5 years before 134a would be out in only most 1993 model year vehicles.

    So the idea is to eventually shut down compressor to save it, it's warning could be off but must say IDK for sure if that's compatible the pressures are higher for 134a.

    Oldsmobile of then! Any new tricks tested on the Olds, the Cadillac version would follow if a success out there.

    Other and hope OE stickers are still there a later Cadillac CDVille customer/friend replaced compressor. It wouldn't kick on again that general era you disconnected battery- for a couple minutes had a grace period it would or should and cut off again if all wrong.

    IDK if you can get sensors new or NOS can say OE stuff worked without changing them but OMG they were newer cars R-12 spiked to insane costs.

    Last don't just go adding refrigerant it takes lots of knowledge plus all temps to DIY that.

    I know of some issues with these hands on or the Cadillac the Olds could change things mid model year so serious searching for specs even tough.

    Have the paper on this car no promise it's correct - listed below:

    OE Spec shown:
    * Holds 38 oz of R-12
    * Holds 8 oz of mineral oil. From zero for both. Adding is knowing what's left unknown unless counting from zero.

    You may or will need pro help for warnings and failsafe features and the warning lights first it should soon shut down? Sorry, nothing for sure,

    MetroWest, Boston


    • #3
      Sorry for two posts on the same car. Sensor reads "low" then "very low" so something to do FIRST.

      It may be right and still blow cool air at max request even climate controlled. So check that output temp, center vent. Should be able to do 45F or maybe less not under 40F for long. Plain meat type thermo or accurate probe.

      If not the warning is real (likely) it's low on refrigerant. That demands finding the leak. Your call dyes, sniffers (my choice) engine off check connections, condenser best you can and compressor's shaft seal is low in belt system oil evidence or sniff it out.

      Then run it check interior vents = evaporator - nightmare if so it's old might last another 35 years better metals.

      Good luck some pre checking for any leaks even the ports for servicing it know these do depends on seal in the cap not all the same if leaking get the Shrader tool I just let most spit loosing + before any loss just snug it up ALL worked again,
      MetroWest, Boston


      • #4
        Some additional information on the issue. I bought the car September of 2021 in Pennsylvania. On the drive home to Michigan, in Ohio, the “Low Refrigerant” warning came on. I pushed the button to dismiss it, and turned the climate control off for the duration of the trip. The next time I took it out, I turned the a/c back on and it started blowing cold and the the warning did not come on. Since then, when I drive it, the a/c always blows cold, lower than 40* F at the middle vent. Sometimes the warning comes on, sometimes it doesn’t. Sometimes I get the second “Very Low Refrigerant” warning, sometimes I don’t.


        • #5
          OK, so this car is in Michigan? Big state so assorted climates expected, Ohio too and PA. I'm inland not too much west of Boston can do the full assortment too always (so far and I'm not that young) home base to me.

          So if sudden fog IDK the lakes or just because that will trigger A/C on almost everything with factory A/C - so said heat dryer air is faster? So off with A/C may not be??

          The 2 stages of low charge has me thinking. CONDENSIBLE gasses change pressure quickly by temp. In containers or the vehicles. Under pressure and certain temps it's a liquid to evaporate. Just fun facts.

          So how this knows it low is measuring temp around it, temp at a switch/sensor combo and still guessing a quick slow down or traffic after steady driving whole engine area heats up.

          Sorry I fail at being concise but it's a total study of it's own that any of compressed air being a liquid to evaporate all at the right place and time is really an engineering feat. Change of RPMs then wind speed coming thru grills!

          If way off leak is why the larger amount system holds if perfect can vary and still blow cold or need to accurate below 40F evaporator, then thru ducts could be close it icing up from being low!! Yes - but those usually come along with no airflow or poor and or if using A/C shut off car make a huge puddle of water but not drip when operating either.

          Factor all include humidity MIchigan isn't ever deadly dry TMK.

          So what do you want to do? Buy some tools or some rentable. It's February temps to test it out without the big buck machines is near impossible.

          I don't own them dang A/C work about quits off season get that junk out of the way other types of work much more needed for about all I know out there. I can heat my shop pretty hot but the gas in bottles takes forever so if not mandatory delay the work till predictable.

          You probably can't just unplug it as that may screw up electric fans still needed or in system's brains not to come on?? Can't know an '88 Olds, high end model.

          Last and a repeat for now is seriously avoid adding refrigerant till you know it's called for, TOO MUCH IS A DISASTER,
          MetroWest, Boston


          • #6
            Yes, definitely not adding any at this point. I was just wondering if maybe 134 operates at a lower pressure than 12, so the sensors aren’t picking up enough pressure and just think the refrigerant is low. If that’s the case, then I would think different sensors may fix the issue. But that was just a SWAG on my part as I don’t know much about the different refrigerants.


            • #7
              For a while it's just 134a that matters also vs R-12. Wild guess next will be 152a is closer to R-12. Hope I can find the pressure chart it's here will post it in this post when I find it. 134a is higher pressure, both sides at a given temperature with lower BTU power so compensated with ever more efficient heat transfer parts - condensers are most of the key vs tube and fin - you see the tubes - those lasted well were fixable. Back in a few it's late/early depending on who's awake?
              MetroWest, Boston


              • #8
                New post site is giving me fits.

                Top post here shows chart whole thread worth the read. Seems like a physics and sciences class - because it is! This area of understanding isn't for everyone is also why as a trade is costly..........

                > https://forum.aircondition.com/forum...pressure-chart <
                MetroWest, Boston


                • #9
                  Don't add any sealer or refrigerant containing sealer !!!! Ever !!! Most of those "single can with gauge" things contain sealer and are worthless.....


                  • #10
                    Cusser, huge THANKS and any reader. Unused (yet) found a can, 18oz does have a gauge says NOTHING about anything but 134a. Is that a lie? It also used the color chart has #s too so IDK have all I need forever now virgin new.

                    Anyone! READ BEFORE YOU BUY!!
                    Last edited by Tom Greenleaf; 02-11-2023, 12:48 PM.
                    MetroWest, Boston


                    • #11
                      Originally posted by 78starfire
                      Yes, definitely not adding any at this point. I was just wondering if maybe 134 operates at a lower pressure than 12, so the sensors aren’t picking up enough pressure and just think the refrigerant is low. If that’s the case, then I would think different sensors may fix the issue. But that was just a SWAG on my part as I don’t know much about the different refrigerants.
                      134a pressure at freezing is lower than R12. The question you are asking is going to be how does the "low refrigerant" warning work. That is going to be something unique to GM products about that year
                      When switching to 134a with CCOT system, which all GM products were, at that point needs the cycling switch changed for the refrigerant used.
                      Later years use a pressure transducer for low refrigerant protection, but unless I am mistaken, they weren't in use that early.
                      So how does the warning system work? I think you really need a manual to understand the system.
                      I'm going to guess, as automotive isn't my area of expertise. I would guess the climate control system looks at how many times the compressor cycles for the input air temp and makes a rough guess at what the state of charge is from that information. If that is the case, as long as the correct cycling switch is used, the system should work. However that is only a guess, as how the system determines state of charge.
                      The higher end "climate control" systems vs. the "dumb" fan and temp levers" are complex and more trouble than they're worth as they age. Exactly when they get up in years, is the exact time when parts for them are discontinued. With manual controls, you can "rig something up", not so with something you only set the temperature desired.


                      • #12
                        Olds: History now there was an OLDMOBILE only factory in Framingham, MA 01701. I abut the now city.

                        Knew of a few folks who either had worked there or close enough to build or buy/order a car not offered or an option from a check list.

                        They (other plants??) did make few or one of a kind cars. I owned 2 of them 1968 no "Ninety Eight" emblems just "LS" had factory anti-lock brakes said so on the brake pedal!

                        OMG they worked had a panic stop almost threw me thru the windshield and DID NOT LOCK A WHEEL! what? factory 4 piston disc brakes unavailable TMK for general production. Another 1970 with over legal powered Rocket 455 than you look up. On purpose just do it?

                        These cars bought new I was second owner.
                        Not faked rather didn't really want to mess up an assembly line for ONE different but did if you had the pull.

                        This subject car is now old is a maybe so few not easy to find specs as a "production" car.

                        Was at a private viewing also there to buy 100s of cars in Maryland saw new cars one of a kind many from founder of Domino's Pizza quit cars went insane (totally messed up) or something dumped them all privately or IDK family did?

                        Until this thread never heard of partly low and then lower for refrigerant did work on a Caddy with a light said something not this exactly.

                        Point is that I've seen them dare I say the rules were to destroy prototypes that were not sold did get out lost out there where it was to retrieve it to destroy? This is actually a bit newer for those games,
                        MetroWest, Boston