On days that start cold, but get warmer due to sun exposure, etc. many of us start the day trying to get the car warm as fast as possible, but eventually turn the whole system off. Now, I just turn the system off, and don’t bother adjusting where the heat knob is adjusted to. My husband and my father turn the system off, and turn the knob to cold. I argue that it has no effect, once the fan is no longer blowing air into the passanger compartment the temperature setting will have no effect, and it is just a psychological thing. Am I crazy for thinking that there is no difference?
It depends on the car. The older style General Motors cars, for instance, relied on the ram effect to put outside air over the heater core (a little radiator) and you did not even need the fan to get warm air in the car when driving. Those cars would definitely need the heat control moved to off if you did not want the heat. On more recent cars, with the heat control on “Hot”, a very little hot air still finds its way in with the fan off, so you might want the control on “off” if you really wanted to be cool.
Your father and husband probably grew up with the old style system, as did I, and would automatically move the heat lever to cool or off when the weather warms up during the day. So, NO ONE IS CRAZY, and leaving the heat control on hot does not heat up your car too much.