Chrysler Repair: Heater blows cold in defrost mode, dodge intrepid, water vapor

Question
Mr. Finston
  I have a 1996
dodge
intrepid 3.5 engine.My heater workes fine until I move it to defrost, then it blows cold air. I have watched all of the doors work properly and I have also tried two manual control panels from a salavge yard. Is there anything that I am missing that is causing this problem? A new control panel from the dealer is 345.00.

Answer
Hi Anthony,
Yes, you are "missing something". The windshield defrost function is designed to be done with cooled air because ambient air that has been drawn in and cooled contains less moisture than would warmed air, so when it hits the cold windshield less water vapor will condense on the windshield and so it defrosts (evaporates) the mositure on the glass more effectively. So there is nothing wrong with your heater system.
Roland