its just weird, ill have the ac or heater off and the blower will be off, however air will still come through all the vents. its strange, i do have a P0441 code thats been on there for a while. i dont know what to check though

 

That's supposed to happen. There will always be some airflow thru the system. Makes sure that you don't get smoked out.....

 

The only time the incoming air door is closed is in recirculate or off. Any other position it is open and air pressure from movement will come in the cab(even if the fan is off).

 

Recirculate uses the air within the cab over and over(better for A/C), but any other selection will allow outside air to blend with the heating or cooling. When it's a cool day that I don't need A/C, but just cool enough to to keep the windows up I just drive with the vents open and the forced air from wind resistance flows through the cab, keeping it at the perfect temp.