Is it neccessary to change your vent settings in idrive from blue to red when you are transitioning from A/C to heat? If I don't, my vents blow cold air. Surely we are not suppose to make this change everytime we change from A/C to heat or heat to A/C.

Also, in between the red and blue vent settings [in idrive] there is a white line. What does that do?

Last, why does the A/C come on automatically in Auto mode, even when you are trying to heat the car? When I turn it off my windows fog so am I suppose to leave it on when heating?