1965 Dodge Dart 270 wagon

Your wagon uses the hard-to-find 4 position switch? Interesting as the complete 65 factory AC system I recently bought uses the 5 position switch as does 2 other factory AC set-ups I have had.

IIRC early B Body owners complain the 4 position switch is made of unobtanium. It seems they used the same/similar switch for heat/defrost as well. Their solution was to try and rebuild the switch (vacuum nipples breaking off is the chief complaint).