I work for a Mopar dealer and back when R-12 was king, we would have to use a vacuum pump to clear the a/c system of water. The pump would pull up to 29" of vacuum which is high enough to boil the moisture out of the system. The a/c machine we use now is a recycle machine with a built in vac pump that still pulls 0up to 29'. My guess is that if the Harbor pump will pull 29 then that should be suffecient, but I don't know what resin vac formers pull down to.