The only difference between A/C and MAX A/C settings is that in MAX A/C, the inside cabin air is recirculated instead of being drawn into the cabin from the outside via the air filter.
If the normal A/C setting works properly, then there is a restriction in the air plenum located behind the glovebox. I'd suspect that more than one napkin was injested..
If the normal A/C setting does not work properly, then there may be a problem with either the temperature blend door or (more unlikely) the refrigerant charge. Since you described that the system does, at times, work well on A/C, I'd suspect a temperature blend door fault.
Steve
