Automotive Air Conditioning Information Forum

Watching Rainman Ray's videos when he charges up a system. At the end, he does a hose compensation function on his machine to add the amount of freon in the hoses to the system. He's saying it's something like .32 lb of freon. Is that possible what with a 1/4" i.d. hose maybe 6 foot long would contain that much freon? I thought it would be just a negligible about. How much could a couple cubic inches of gas weigh?

atikovi wrote: ↑Thu Jul 20, 2023 7:40 pm Watching Rainman Ray's videos when he charges up a system. At the end, he does a hose compensation function on his machine to add the amount of freon in the hoses to the system. He's saying it's something like .32 lb of freon. Is that possible what with a 1/4" i.d. hose maybe 6 foot long would contain that much freon? I thought it would be just a negligible about. How much could a couple cubic inches of gas weigh?

I saw that video too. Rainman Ray is a very smart guy. I'm not a professional mechanic (excepting my 1.5 years as VW mechanic in the mid-1970s), and I learn a lot from watching his (and Eric O's) videos, helps me on our 6 vehicles.

Ray DID state 0.32 pounds (that's over 5 oz. !!!), but I believe that would have to be liquid refrigerant weight, and his fancy machine adds the complete charge as a liquid and can compensate for that. Most of us home-garage guys may add the first can or equivalent as a liquid, but we then add the remainder as a gas with the compressor engaged until the system is filled to optimum weight. So no way would 0.32 pounds of gaseous refrigerant be contained in a hose.

Like all of us, Ray makes mistakes sometimes....

I think Ray's calculations are off considerably. That said, I've never tried to calculate exactly how much refrigerant remains in the hoses after charging a system. But presuming the compressor is running with the engine at about 1,800 RPM, the way I clear the hoses of refrigerant after charging, using a Manifold Gauge Set, is as follows:

1. Ensure that the valve at the charging cylinder (yellow hose) is turned off.
2. Turn off the adapter thumb-wheel on the high-pressure side.
3. Ensure that both MGS hand-wheels are fully open.
4. Fully open the thumb-wheel on the low-pressure adapter, and any refrigerant vapor remaining in the hoses will be drawn into the system's low side.
5. Fully close the thumb-wheel on the low-pressure adapter, and proceed to remove the adapters, MGS, and hoses from the system.

John's method is what most of us use. The only hose with any meaningful amount of 134 is the high side, which is full of liquid under pressure. His method allows you to bleed the amount that is in the red hose back into the system via the blue hose. So if you used a scale to charge, then the full weighed amount that was removed from the cylinder ends up in the system as it should.

FWIW I measured the amount of 134 in the hi side hose once by weight and it is 2 oz

Yes, John's method works just fine. Allow the engine to draw in the majority of the refrigerant in the hose is the way to go.