Airportable

Is it fair to follow this reasoning? The windscreen clears the fastest when the heater matrix is hot & the blower on max. First thing on a cold morning you only have the blower but if you push more air across the screen it will clear faster. However the blower is restricted to the voltage at the terminals, jack that voltage up & the fan runs faster, too much & it’ll blow. I have a similar motor on the bench at the moment running happily at eighteen volts & it’s no more than aired. Next move is a DC to DC up converter into a variable controller & dispense with the rotary switch.