onehundred80,

I'm not quite sure why you referred me to that document. Yes, it has good information. Nearly all of which I have read previously. The problem here is that the "Fan Regulator" has gone bad and there are quite a number of owners in all three brand categories that have replaced more than one of these units.

I am making sure there is no special function for this unit other than translating 0-7VDC at low current (control signal) to 0-12VDC at high current (Fan operating power). When I talk about mapping out the circuit, I am referring to the internal circuit in the "Fan Regulator" itself.

I have come up with a simple PWM circuit that may be a cheaper solution. Without putting a scope on the fan power while it runs and see if it is already PWM, I have no way to confirm the ELMOS chip on the unit is a dual timer or something more complicated.

Anyone here able to put a scope on the fan power side of a working unit and see if it's pulsed DC or flat DC?