[wjy]

Being a controls engineer, this behavior always drives me crazy. I love to observe the temperature controller do its job. But it does depend on the car.

A good controller will blast the heat at max until the temperature gets close to the setpoint, then back it down. Turning it up to 90 does exactly nothing extra for you, but does end up overheating you.

However, not all cars have good temperature controllers. My wife owned a Honda Accord a while back, that was simply awesome at this job. We never, ever changed the setpoint in that car because it just worked great.

The Subaru Forester we have now is much, much worse, and we do end up fiddling with the setpoint because the controller's not doing its job well.

[foofoo55]

Being a controls engineer, these assumptions of thermostatic perfection drive me crazy. The things only measure air temperature, not that of the seats, dashboard, wheel, etc. When these objects are cold a person will feel colder than if they were the same as the air temperature. See also thermal conduction and thermal radiation. Also, that thermostat is located where? At the driver's fingertips? Their rear end? Not likely.

So cranking the air temperature setting beyond the desired air temperature for a while will indeed get the cabin more comfortable quicker.