i like control the speed to extend the pump life, for an idle use i don't need the pump run 100%. at this point i don't know the utilities about the 3 pin, if i can only check the speed...The pump has a 4-Pin Molex connector for power. The 3-Pin connector is only for reading out the rpm of the pump. You cant control the pump over that 3-Pin connector.
Why do you want to control the pump?