Air conditioning decreases output by 40-60% after 80-150 miles of constant driving on expressway during hot days [above 85 degrees] and high humidity [above 70 %}. decrease in volume of air from vent, with no change of air speed control and much warmer air. Air recirculation button in "off" position.have to stop car for 10-15 minutes for evaporator to defrost and drain on pavement. Afterwards, ac is cold for another 60-100 miles.two different VW dealers indicate no bad codes for air conditioner. Continued to occur five more times in summer.

- Lawrence, MI, USA