We use the Hayden adjustable controller and put the probe in the radiator, just below the outlet and a couple of inches away from the tank. The controller is adjustable and also has the an override normally used for the AC. We hook it to a switch on the dash for anytime you want to run the fan full time, open track or autocross between runs. We adjust so the fan kicks on an off where it keeps the engine cool but does not run on and on after engine shut off. HTH, Cheers Richard.