My trusty old circa 1993 Rotunda (Robinair) R12 Recovery/recycle/charging machine took a big gulp of 2 part sealer a while back, may it rest in peace. For R134a, I used a recovery only unit, manifold gauge set, vacuum pump, and #30 cylinder.
I recently purchased a used White Industries 1234Xl, dual refrigerant machine. It works great with both refrigerants and has really simplified my small side business catering to the local collector car crowd, family and friends. I'm as happy as a kid with a new toy.
In getting familiar with the machine, cleaning it up, etc., I noticed that there are no scales for the virgin refrigerant cylinders. Now that I think about it, the Rotunda unit didn't have a scale either, but it would charge by weight. So does the new machine.
How do these machines "weigh" refrigerant, or do they?
I'm familiar with the correlation between pressure and temperature when dealing with refrigerants, but...weight?
Oh Boy good luck....they use timers, based on temp pressure relationship-I never liked them for the very reasons you suspect. They assume a lot of flow things- I would think a tank valve left partially closed would really screw up the amount that enters the system....but they sold a ton of those machines- so maybe they are alright....
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
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