Steve, can you explain a bit more? I certainly understand regulating the speed of the motor by varying the ground side/path of the motor, but something doesn't add up.
If the voltage drop to ground is 1 volt or less at high speed, what is the "blower motor voltage" shown in the diagnostic mode of the climate control head? Maybe its not really blower motor voltage?
If hot side is 12-14 volts, how can "blower motor voltage" only be 4.8 volts with a 1 volt drop?
Thanks much, KenP