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'Depends on charge weight, PAG oil volume, the compressor design, compressor RPM, etc. There are so many variables that go into an AC system.'

Yes, BUT, one thing people should keep in mind is that although those things can change, the gas properties do NOT, they are firmly locked into the gas and pretty much stay the same. I've found the biggest error is usually oil amount, everybody gets scared and overoils and it doesn't take much at all to tilt the cooling toward crummy. I use varying amounts of gas at times and, still, charging to the same rough pressures by temps has every single system working like gangbusters, they will freeze your butt off. I did R12 the same way and used same numbers over and over too, I have never charged by weight ever and doing it for 45+ years now.
 

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'...you don't truly know how much of the can is actually freon and how much is propellant.'

I for one am a bit lost on that one as the refrigerant IS the propellant, both R12 and R134A are used as propellants for a number of other non-a/c uses. There should be nothing there except for the refrigerant, or any oil or diagnostic material added for other things. A major requirement of any propellant is that it vaporizes easily at pressure release under room temps, refrigerants do that by nature to be good choices. They lower pressures required in the containers to make them safer yet still provide the pressure needed to get work done. The only propellant in a can of refrigerant should be a pressure of about 75 psi or so.
 

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I took a semester on AC systems I've used the machines I had my AC license for automotive applications.
You absolutely can recharge at home.
A machine is nice especially a good one it makes life easy, but you can definitely have functioning cold air conditioning without it.



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I see over oiling constantly, especially with the UV dyes. One day it looked like a scene from Ghostbusters in one of the bays, just neon green on the floor everywhere like someone murdered slimer and he bled out 😂
I think one day we measured a cup of oil in one vehicles ac system between the lines and condenser and so on. I guess people can't measure in ounces these days

The machines we use obviously go by charge weight but we look at system pressure too and tweak accordingly. Going by weight gets it right 99% of the time on modern vehicles.
 

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this is very true, however I typically see customers using the cheapest recharge kit out there and you just have to kind of stare at them. Granted every single one wound up having a leak somewhere in the system so it was kinda like hey, you're gonna need a bigger boat. Or fix the leak.

I guess I just never trusted doing it at home? Granted I remove ac from most of my cars so I'm "that guy" lol. Like right now my SVTF has been sitting so long the compressor might cycle for 2-3 seconds and then shutoff. I haven't done any diag on it but I might just remove it
 

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One last thought, I note that everybody does a/c pressure checks by vacuum. While fine most of the time you can have a leak under pressure that does not show under vacuum, o-rings being the funny things they can sometimes be. BTDT.
 

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I've also seen that. I try to get my guys to do a positive pressure test 😉
 

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Man everybody overoils, I saw so much of it when in parts I began to understand how so many of the systems are messed up. I once did it myself way back in my early years and simply stuck a brass tube into the accumulator port to pressurize the system by air to pump the extra oil out, and then pulled a vacuum and did not change the accumulator at all, in fact I've never changed one ever. If no leaks and the vacuum is right there is NO air in the system to cause issues and I've never had corrosion problems ever. That overoiled system went back to freezing very well once the oil amount was dropped and I had a 'duh' moment over it. If you think about it, most systems if not leaking can use quite a chunk less of oil, and now looking at oil charge amounts on later cars I'm thinking even the OEMs are lowering oil amounts to both let the a/c spin a bit easier for mileage and to lower materials cost on the assembly lines. Another sneaky way to get somewhat greater increase in a/c work too.
 

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Yeah newer cars are using virtually no oil in comparison. I think maybe an ounce on average iirc
 

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My AC instructor was in his seventies he worked for a Toyota dealership for a long time, and was also a Air Force airplane mechanic. When we used the machine if we pulled out excessive amounts of oil we would only put about half of it back.

In his opinion during a vacuum you shouldn't be pulling out any more than 1 oz of oil. So if we pulled out 2 or 3 oz of oil we would only put about 1 oz back.

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That's valuable to know, I've wondered about it myself. The oil sitting in low spaces should hardly come out in the vacuum at all. Unless too much of course to get sucked up as the vacuum 'reduces space' so to speak. That action will move the oil around but the only amount coming out will be that which was close to the vacuum sucking point. Most people think a vacuum removes 100% of the oil but it does in no way, it would of course if it were a 'perfect' vacuum but no such thing exists except maybe in space. Maybe not even there as nature abhors a vacuum. In a black hole?
 

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as far as I can recall pulling a vacuum will never get 100% of the oil out, too many bends and low spots. GAS especially, they seem to love to hog all of their oil in the accumulator. I can't remember the model we use at my shop but it actually gives you an oil measurement of what it pulled out during the evac and then of course we monitor the oil level as the machine keeps the system under vacuum. This of course is dependent upon the system being sealed and having no leaks, which we rarely see.

In Georgia it goes 2 ways

Cold weather: my car won't start and the heat doesn't work
Hot weather: my car struggles to start, my car overheats, and my ac doesn't work.

Hell I think we avaerage 5 or more ac diags a week lately
 

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Discussion Starter #33
OK, that sounds good.
I haven't added anymore Freon yet.

I didn't know there was propellant in the can. Thought in a liquid state, it was already pressurized since gases go liquid at certain pressures and stay that way. I kept the cans right side up during charge.

I haven't even used it since the charge. Really just want to see if it holds a charge first, or just waiting for a really hot day, perhaps October or a trip across the Mojave.

Thanks, appreciate the help!
 
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