The other day I was assessing the operation of the heater fan in my wifes mini (K reg 1.3 automatic). It would seem to have two modes of operation, off or very noisey. Sadly, the fan doesn't seem to push air out of the winscreen ducts very well. I guess this may well be due to the resistance caused by the small diameter pipes from the heater matrix and the resistance caused by the heater matrix as the fan trys to push or pull air through it.
Do heater fans exist that have more than one speed? Eg. Off, noisey & very noisey?.
The mini has a tube from the heater fan/matrix to the drivers wing to source fresh air. I wonder how effective this is? Maybe things could be improved by fitting a fan inside the tube near to the air intake vent to improve air flow. This fan could be more like your traditional propeller fan and maybe more efficent at pushing air than the water wheel design that is in the car. If it is more efficient then it can rotate slower with less noise.
Another idea could be to mount small fans directly over the tubes to the windscreen vents, hopefully giving a better air flow.
Any other ideas?