I have a fan (for cooling Peltier device) that runs on 12VDC 0.28A with impedance protection (KunPenz FS8025HD1). I would like to reduce the speed of the fan about half, in order to reduce sound noise generated. I have tried both adjusting the supplied voltage and current (using a 10kOhm potentiometer). It seems to me that either way it is really sensitive in that either it runs 100% or nothing at all no matter how careful I am in turning the potentiometer. Why is this? Do I need a smaller potentiometer, is there a way to calculate how much I need? Or am I out of luck because the fan has some internal IC ensuring it runs 100%?