This is a nice feature which helps keep condensation from dripping down into the HVAC ducts after shutdown. I wouldn't have it any other way now that I've noticed it. Mildewed ducts SUCK!Do any of you ever for whatever reason sit in the truck for a few minutes after turning the engine off? You all of a sudden hear servos moving without touching anything maybe they go back to a neutral position and that is one where the heater core is exposed to the air flow. Once the system is energized it goes back to the A/C on setting.