Quote:
Originally Posted by Frank Lee
The difference in warm-up time between heater control cold or heater hot can't be much, can it? And after the engine is warm I don't see how heater control knob position can affect mpg at all.  However I can see a negative mpg effect from the alternator load increasing with higher blower settings. |
certain cars have a ventilation system that forces air through it due to high pressure zones on the blower intake area, so the faster you go, the more air gets forced through it with the blower not contributing to the airflow. if you have the position selector set to move air through dash vents, go 50MPH or so with the blower motor off and see if you can feel air movement. if so, it won't be much, but it will be something.
others have a completely "sealed" system that has absolutely no airflow with the blower off.
others yet have systems where the blower motor is on at all times, although at a very low speed to where you usually won't be able to hear it.
it's all dependant on how your HVAC system was designed.