A/C Charge by Myself

In the old days, shade-trees would fill w/ R-12, then blow some off to sweep out air and moisture. That was in the days of 25c Freon cans and Freon BB machine-guns. Seemed to work and the filter's dessicant probably captured any remaining H2O. Certainly pumping down to 29" Hg w/ a Mighty-Mite hand pump is better than nothing, especially on a hot day w/ engine in the sun. You can get half-way there by connecting to intake manifold vacuum (best after a booster charcoal filter & check valve), using a valve to isolate. R-134A is much more problematic w/ moisture since PAG oil absorbs it and forms corrosive acids. PAO 68 oil is a better choice, more efficient and works w/ all refrigerants. Seems silly to convert to R-134A today just before it is outlawed. You can vent HC refrigerants (Duracool, Enviro-safe) w/ no more danger to the earth than a cow fart, but the EPA says that is illegal because ... "just is".