What I don't understand is how this "frequency feedback" travels without a complete loop. At 75mph your fan is not needed, and the thermostat/controller would be open, eliminating the path for 12v power to the fan motor. The fan is freewheeling, but the path back to the electrical system is blocked by an open switch, either a physical contact or an electronic switch in a controller. How does this feedback get to the other components if the fan is OFF?