Below is a link to the controller i use....Lots of features, made in the USA. It works flawless so far. 1 Year warranty.
http://www.ebay.com/itm/RADIATOR-FAN-CONTROLLER-85-AMPS-PULSE-WIDTH-MODULTED-FAN-RPM-/251297321625?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a827cd299&vxp=mtr