[tripletdaddy]

A "discharged" or low charged system hasn't necessarily taken on any air or moisture. That won't happen until it has near or at zero system pressure. A system below 45 psi at the low side will not come on, but the system can still have pressure in it, but it has not completely leaked out and may not at least for awhile. If it has pressure, even if it is below 45 psi, how could air and moisture possibly get into it? Only if it is COMPLETELY emptied out to a gauge pressure of zero, due to whatever reason, leak, breach, disconnection, etc., will it take on external contaminants that can be drawn in by the expansion and contraction of the "gas" inside the system due to temperature, sort of like it's "breathing." Otherwise, it will not, and it can not take in anything. It has to obey the physics .