sl; See my notes on ECF here:
http://www.sw-em.com/Cooling_System....ic_cooling_fan
LJD; Top of Radiator is input side, and will be hot any time TStat is open and calling for cooling, so I expect your Fan to be running just about all the time...I prefer to only energize the ECF when Rad does not supply adequate cooling (hot outside air or slow roadspeed), therefore recommend placing temp sensor for ECF in bottom tank of Rad or Hose.
Cheers