when is clear outside no matter what is the temp, I just make sure all i see is green lights and i set the heat to a confortable temp and i have zero problem but if is raining or snowing outside there is a 90+ chance i will need to turn the ac on and ofcourse change the way the air circulate or flow in the car.
is very true what Thooks said above.
u can also try this quick fix, dont talk dont breath