Almost the same analogy is used with interior blower fan. The final stage (hedgehog) gets PWM control from IHKA. The final stage determines the voltage applied to blower fan according to PWM. With the electric cooler fan the final stage is inside the fan housing and the fan motor itself is more sophisticated and complex compared to traditional blower fan motor. So in order to run the cooling fan with direct voltage you would have to take the fan apart and it still would be very difficult to run the motor with electronic commutator with direct voltage.