being into the mood of putting my old car into the "21st century" I'm trying to modify certain mechanical, bulky or simply not cute features with the equivalent electronic ones. so the last think that hit me is the heater blower motor speed control. first I thought that I could change the 2 speed control to a 4 speed by replacing with the appropriate aftermarket resistor along with the needed switch. but then it came to mind that I'd prefer a more electronic solution. given that both blower and resistor are in the engine bay I would like either to totally control electronically the speed of the motor or, if this is far fetched due to the high currents involved, to keep the use of the resistor but switching to be done through some up/down electronic circuit that would feed the resistor, thus eliminating the heavy cables going through the firewall. any ideas would be most appreciated.