A/C amount Freon - 3745

I have a 157 continental Markll with factory air. Can anyone tell me the number of ounces of R-12 it holds . Most cars today take 2 12 oz cans of r-134. I have installed 4 cans of R-12 and it gets cold .The gags show the low side pressure 30 the high side 200 in 95 degree heat here in Kansas. The problem it takes too long to get cold ,so I feel I do not have enough R-12 .and do not want to overcharge. can anybody give me that information and any other advice I should know.

This is the first time I have sent in a thresd,i guess that is the right terminology.

Thanks Donald F Lett

The manual states 6 1/2 pounds.

Unless 57's are different than 56's there is a sight glass in the trunk that should be free of bubbles when the system is full and turned on.

Yes you are right and I appreciate your response. the problem with the sight glass because of the age of the sight glass you cannot see Freon or bubbles because of the acclamation of residue over the glass making the Freon or bubbles not visable. so the reason I wanted the quantity was with the unit pumped down I put in 4 cans 48 ounces ,now I could put in the remaining amount that is specified. So I still need the total amount of FREON. If you know someone in the forum that knows I would appreciate there names and how to contact them.
THANKS
Donald f Lett
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Donald Lett

I am new to forum and have never communicated with anyone . after just sensing a note I seen where I had 3 responses .so I clicked and founf the answer again I thanks because of your answer I now know it is 61/2 pounds.


Donald f Lett

Kewl! And welcome. That's really the key: one you pose the question, then check back to read the replies... Good luck. John

The amount indicated on the back was 6.5 lbs but if R134 is used it is 70-80% of this amount. Yes I have found slightly less was also able to be used as before it was determined actually how much was required in the early nineties when it came out and people assumed you charged an R12 system with 134A the same which was not the case because if this was done IE charging till the glass was clear then you were overcharged. Quite often when the happy amount of 134 wasn't known I had to use a thermometer on the evaporator discharge with the engine at fast idle or if it was off road equipment high idle with the blowers on max and slowly charge until the temperature quit dropping which would indicate maximum efficiency and of course if one was "day dreaming" or neglected to shut off the refrigerant entering the system, the temperature would start to rise. This is how I discovered that some systems would work great with as low as 70% 134vs 100%R12. Sorry for the slight off topic re. 134vsR12 but typically the R12 was until the sight glass was clear and then an additional 1/2 to 1 lb of Freon depending on how large the receiver drier/accumulator is and in the case of the Mark II this drier is massive and is located under the passenger side floorboards. It is massive unless a smaller universal fit or aftermarket drier was installed. The sight glass being covered with a film is not the best indicating a bit of a dirty system but perhaps a very bright light will let you see. Going by pressure also works in a pinch and this is where a pressure chart or the indications on some guages are used IE the higher the outside temperature the higher the pressures of both the low and high side. Also a restricted condenser located infront of the radiator or a restricted radiator blocked with insects can cause the pressures to be too high with poor cooling.
And by the way DID YOU CHECK THE OIL LEVEL IN THE COMPRESSOR THROUGH THE SITEGLASS?? This is located on the bottom side of the compressor and when not running you should see oil in the crankcase of the compressor. A very common mistake which was done on my car when it was recharged with insufficient oil and the damn compressor burned out before I bought mine and try to find parts for an HH Techumseh because I do believe the last year they were manufactured was 1957 and parts are nearly extinct resulting in compressors being parted out!! Also another thing I forgot to mention is the 1957 didn't have this oil level site glass unless an earlier one was installed or a later one installed in a 56. Typically the oil circulates with the freon and if you have a leak the oil escapes with the freon and areas where there are leaks quite often have signs of oil such as fitting/hose connections and the front seal of the compressor. As for the cloudy or dirty sight glass and the oil level, if in doubt use a recovery unit and recover all of the valuable R12 and clean the rear sight glass and check the compressor and if you go this rought drain the oil in the compressor and refill with fresh oil. Consider getting your drier reconditioned as well where they cut it open and replace the moisture absorbing desicant because other than dirt and lack of lubrication, moisture is an enemy of an AC system because water combined with R12 creates an acid not to mention freezing and restricting the Thermal Expansion Valve. BTW a restricted or defective expansion valve will give you low to negative pressure on the low side and poor cooling showing a clear sight glass but low pressures typically low to negative on the low and lower pressures on the high. This restriction can be the result of the desicant breaking down or the small bag containing it rupturing and the desicant circulating through the system and ending up in the expansion valve. A lot of times a small screen was inserted in this valve to catch contamination and would require cleaning. If you choose not to recondition the drier a smaller aftermarket one can be installed but of course depending on how small or large it is will create a reduction in the amount of the R12. Slide under the car and check. If it is the large OEM tank underneath throw in another 2 to 2 1/2 cans to give you 6 to 6 1/2 lbs. 4 lbs is not enough for such a large system.

On the subject of the sight glass--- Mine leaks and some time ago I tried to get it out and apart to reseal it. I was unable to get the nuts on the lines connected to the sight glass assembly to loosen with two large open end wrenches. Not wanting to break the sight glass assembly or damage the nuts I stopped trying. That's where I stand at this time. If someone has encountered this problem and has any suggestions how to get the line nuts to release I'm all ears.

Possibly a bit of heat on the flare nuts might persuade them and if worried about the glass I would warm up the whole assembly with a hair drier or a heat gun on low at a distance to reduce thermal shock. Once warmed up give these nuts a quick flash of heat and try the wrenches again and oh by the way use flare nut wrenches. They are a box end style with a slot to allow the tube to pass through. In severe cases I used vice grips clamped on flare nut wrenches to keep them from spreading but later invested in Snap-On which are superior and a six point wrench. Also place the wrenches slightly apart and squeeze them both together with one hand to prevent bending, and twisting lines or components. If the nuts are even seized to the lines such as the case of rusted brake lines I have heated up the flare nut until it started to glow slightly and broke the rusted brake line nuts loose using a cheap wrench that I didn't care if the heat damaged it and breaking it loose this way saved me from lines twisting off especially if you can't find one right away or want to use the old for an exact pattern. Once they broke loose I would rapidly rock the wrench back and forth while hot to insure they would stay loose after the cool down with penetrating oil used. If I reused the lines I would paint or spray with spray grease or undercoating to stop additional rust on these lines and in the case of the refrigerant lines this wouldn't hurt underneath if rusted. Much kinder to these fittings.are the flare nut wrenches and If you want a sight glass that is miserable to find, try the one on your compressor! Years ago the bananas that shoddily attempted to rebuild mine used a damn sand blaster and were tooooooo lazy and stupid to cover the glass and it was pretty much ruined. Painting it would have been easier to deal with. A leak is certainly no good and has to be solved. I never believed in recharging to limp it along for a month or two especially now with the regulations and price of refrigerant in some locations.

What I will do next is go to a refrigeration supply and see if I can match up a site glass as they are often used on commercial systems and are replaceable with seals. I purchased an HH off of ePay years ago not realizing there were variations of these while still marked HH! The one I got If my memory serves correct was from a Studebaker according to Vintage Air and they mentioned the site glass was horrible to find. As it ended up this mystery HH Techumseh was like brand new inside and I never had the heart to part it out. It has a much better design clutch than what the Mark uses with a magnet bolted to the compressor instead of the brush style. It is complete but suffered rust damage. If your seals are worn out you can probably ubtain some from the same type of supplier in your location.

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

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.