There is 12 oz of Freon , ie R134A in this 12 oz Can below, right?

On another website I was told that are actually only 10 oz of Freon in a 12 oz can as shown below ( please disregard the Brand Name, the picture is show only to depict can size )
I am preparing to recharge a non-Mercedes Diesel AC system after rebuilding the compressor myself.
Honestly I think the guy who told me this, who is very very sharp and good at electrical issues, is perpetuating a urban legend. I would believe him if the can was loaded with Dye, Oil sealer and it said so, but in my book a 12 oz can of Freon contains 12 oz of Freon. This isn't the first time I have run into someone who is sharp and yet unwittingly perpetuates an old wives tale.



( please disregard the Brand Name, the picture is show only to depict can size )

12=12.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

What he may be referring to is you can only get 10 oz of freon out of the 12 oz can. I don't know a lot about ac systems, so this is just an educated guess. The pressure inside the vessel can't be reduced lower than the pressure of the system being charged (unless the system draws a vacuum on the can), there must always be some material left in the can. If the compressor "sucks" freon out of the can, then you should be able to remove all the contents. But if you are relying only on the pressure inside the can to deliver the contents, you won't be able to remove everything.

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Keep everything as simple as possible-but no simpler--Albert Einstein

He was right.

I guess that explains why I always wondered why everytime I really thought I had squeezed every last gram of Freon out of a can and then disconnected it from my charging hose, I would always get a ""Whoosh" of freon escaping at the end.

I think this shows the dangers of attempting to charge by the volume of the Freon canisters. If you have a way of charging by weight, this becomes a non issue. However, I don't see how you can do this with the small cans.

honestly, although there is some leftover in the can, I bet it's less than 1/2 ounce. Besides, you should charge to a pressure, not a weight anyway.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I'll bet that there will be a few folks who will take issue with that one.

If you get all the liquid out you have almost nothing left in the can.

12oz = 22 cubic inches. 22 cubic inches of vapor at 30 - 40 psi. Cmon how much are we talking about here.

danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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If the brand is not DuPont, then there is no Freon in the can!!!

I agree with Pete that there probably wouldn't be a full 2 ozs left in the can, but you never know. An oz isn't all that much weight.

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Keep everything as simple as possible-but no simpler--Albert Einstein

Well, isn't this why the books show putting your can into warm water when charging your system ? As long as all the liquid is converted there should be very little left over...

"Habenero's First Law of Automotive AC Recharging" I have a pyschrometric chart for Freon, below. Using P= 90 psi ( the pressure at the low side on a typical Car AC system) and Temperature= 90 degrees farenheit ( at 4pm in New Jersey), the chart will give you the Specific Volume for Freon...uh I think...
Next, knowing the volume of the can, we can calculate how much Freon is left in the can. Having just woken up from a nap, my brain feels like what i will feel like in the year 2040, so I cant do the calculation right now..catch me at 11pm when my mind is the sharpest

I thought R134a cans were 14 oz?

R12 cans are 12 oz.

Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E

Are we talking about R12 or R134? Your nightmare of a chart is for R-12, but I thought we were talking about 134. If we are indeed talking 134, then the chart is useless for the current discussion. Would still be an interesting thought experiment, though...

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Keep everything as simple as possible-but no simpler--Albert Einstein

I have no R134 chart, but I don't think the calculated value would be that much different