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Thread: A/C amount Freon

  1. #11
    Join Date
    Aug 2017
    Wichita, Ks
    Thanked: 1


    How much of a hassle is it to convert to R134a? I have access to refrigerant. not so much to R12.
    Paul E Davis

  2. #12
    Join Date
    Aug 2009
    Rosthern, Saskatchewan, Canada
    Thanked: 39


    R-12 is hard to find in Kansas?? That surprises me because I see the occasional person sneak some back from the States in the 1 lb bombs or cans. I call them bombs because if you don't know what you are doing and attempt to feed the R-12 into the system through the high side instead of the low things can happen. How big of a hassle? First of all how good are your hoses? If they need replacement you can get them retrofitted with modern hoses with an inner barrier to prevent the 134 from seeping through. I used to drain all of the mineral oil out of the system and refill it with Polyolester oil which is compatible with R134A and( correct me if I'm wrong ) if memory serves correct this newer synthetic refrigerant oil is compatible with R12 as well. I will research this later. Anyway I would remove the compressor and drain it and refill with the required amount. Usually replace the drier with a new drier and of course "charge" or add an ounce of oil to the drier as well but in the case of these cars, one has to have the original reconditioned or simply install a newer universal fit drier and if necessary use adaptors to the fittings and make an extension pipe or hose because if you look under your passenger side you will see a fairly large tank AKA receiver drier which is both a reservoir for extra liquid refrigerant as indicated by the tank as it appears and it also contains a sack of desicant which absorbs one of the enemies of AC moisture and at times a bit of a filter in there as well. A universal drier if smaller will mean less refrigerant will be required and the fact that it is a reservoir provided a bit of surplus if you had slight leakage due to a tired compressor seal or hoses but I tend to be very anal (fussy ) about leaks. Usually with R12 when charging one would look at the site glass and add till it became clear and another 1/2-1lb of refrigerant that would end up in this drier. When 134 first came out it was recommended that a complete flush of the system was performed due to the other types of oil used such as PAG not being compatible with mineral oil but Poly will mix with smaller amounts of mineral. Some say just add Polyolester but I never really liked to do this especially if you don't know how much oil is in the system already and excessive amounts aren't good. Besides if the system is a bit grungy from a compressor failure or moisture contamination it should be flushed throughout the entire system anyway. There is a rule of thumb for how much oil should be added as well IE depending on the size of the condenser in front of the radiator 1-2 oz., the drier typically an oz but ours is massive, the evaporator depending on how big or small it is, again and oz. or two and the other determination other than manufactures spec. was the diameter and length of all the hoses and pipes. Yes there is oil in the compressor but the oil also mixes with the refrigerant and circulates through the system. Next you get some R134 charge/guage port adaptors that are screwed onto the R12 guage ports because the R134 guages have a snap on quick coupler and are different sizes to prevent the wrong hoses being connected (remember the bomb description). Next IF your system is totally stock with an OEM drier and no modifications then you would use about 75-80% of the original recommended for R12 charge of 6.5 lbs which would be 5.2 lbs. When R134 came out there were many horror stories about "Oh your original evaporator and condenser will be tooooo small and you will need to install larger�� or your system is just toooo small and won't work blah blah blah and other stories including thoural flushing etc. (before the Polyolester came out) but in reality when this refrigerant came out most of us didn't realize it needed less and everybody would charge until the site glass was clear and add a bit more. R134 has one characteristic compared to R12 and that due to less being required, if you put in the same amount as R12 your system would become inefficient hence the former belief that the system was too small to convert. When R134 first came out with all of the complaints after the conversions it was realized we were overcharging. The rule of thumb was we had to determine MAXIMUM EFFICIENCY and in order to do this back in the dark ages was to stick an accurate thermometer in the discharge of the evaporator and place the engine at high idle if it was a piece of farm equipment and SLOWLY charge the system with the blowers on max watching this thermometer like a hawk. I would slowly charge until one would see the thermometer stop dropping (with the thermostat not cycling on and off of course) and if one was day dreaming of distracted and started overcharging you would actually see the discharge temperature start to rise which indicated the overcharging was causing the system to become less efficient. And this would require excess being recovered. This is how I discovered that some systems would work great at 70-75%. Also your sight glass will have slight bubbles or a milky or cloudy appearance due to the reduction and a lot of the newer systems don't have site glasses anymore (usually found on the drier) but the driers usually came with them anyway and after a while I could tell I was very close by the site glass by seeing it so many times. Now as for the amounts of oil etc. if you have a modern compressor installed they use different amounts of oil and I had to have special dip stick guages to insert into the compressors to check or you totally drained the compressor and carefully measured what was needed and filled. Also keep in mind that your pressures are slightly higher with this refrigerant compared to R12 and at times when charging R12 the pressures would be slightly higher when getting close and would drop as the final amount was reached because now the evaporator was getting nice and cold which reduced the pressure a bit. Also if you are using a modern compressor, the throttling valve can be eliminated and a thermostat can be hidden in the system on the evaporator and the compressor can be cycled on and off depending on how cold your evaporator is. The original clutch on these cars has one major flaw or weak point I was told and it is DO NOT TURN ON THE AC COMPRESSOR WITH THE ENGINE RUNNING AT HIGH RPM!! Apparently it is hard on the clutch to subject it to the shock of engaging it while the engine is running fast and should be engaged while idling. This system doesn't use a thermostat but the throttling or recirculating valve to control the temperature and the compressor is always running once switched on. Is it a hassle as you asked? No not really but there are preperations that should and have to be done for the system to work properly and I have no intentions of "modernizing" my system by installing a newer York, Sanden, or modern Techumseh compressor. I have all of the parts slowly accumulated to rebuild my 52 lb HH Techumseh compressor that looks like an air brake compressor from a Semi trailor truck. My only disappointment was the choice of clutch Ford used compared to the clutch on the Studebaker HH Techumseh I have. It is older but is a modern design that can be cycled on and off with a thermostat. I was surprised when I first saw this compressor and this design of clutch dating so far back. Yes the original compressor should be able to handle R134 which is why I will keep it in my car even though it is dificult to get parts for.
    Last edited by Don Henschel; 12-18-2017 at 03:14 AM. Reason: Forgotten information on an already long winded post
    Two-Tone 05/16
    1950 Mercury Sedan

  3. The Following 4 Users Say Thank You to Don Henschel For This Useful Post:

    jdsnoddy (12-18-2017), Keith W Colonna (12-26-2017), Matt Cashion (12-18-2017), rickswrecks (12-19-2017)

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