I think you are imagining things. Hoses leak, and oil boils off refrigerant. I doubt you can pull a true 200 microns on an automotive system and get it to actually hold. Just the oil in the system alone is likely enough to trash that
Well, yes, 200 microns might be a little optimistic. Force of habit with some of this process stuff with -40 evaporators. Specs for VRF is 50 microns to hold.
A good shaft seal is always the trick. Good hoses don't leak, as you well know. But I was always surprised the auto industry doesn't adopt nitrogen for test and purge like the rest of the HVACR industry. But I stand by what I said - a standing pressure test at 200 psi.
