My main drive was to make sure that I can always make cold are blow out those babies. I don't worry that much about the heat. I did notice that when I want the heat or defrost and those particular damper doors open there is not that much force out of the open center dash vents and again - you can shut it off all the way with the manual shutters. The 126 is the same except for the difference in the way you shut if off.

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Jim