Blowing Cold

I use HC refrigerant (Duracool) w/ PAO68 oil in all my vehicles, even my 2002 Chrysler (after its AC clutch failed). Don't believe the claims from unschooled that it can "explode", since most never took a graduate engineering course on combustion. Works slightly better than Freon. I have an underdash knee-knocker in my 3 1960's Mopars since none had factory AC. They have an integral brass expansion valve similar to old Mopars. A custom climate box w/ AC would fit nicer but then couldn't use the dash knobs. I installed a water valve in all, vacuum-operated 1-tube from a 12V vac switch actuated when the knee-knocker is "on" (ran wire from inside into engine bay via unused bulkhead terminal). Probably overkill since the heater fan isn't run during AC anyway.