[mclairmo]

IMO, you want the electric fan on as little as possible to prevent overcooling, to extend the life of the expensive fan motor and to prevent unnecessary stress on the charging system/alternator. The engine temp will usually be higher than the radiator temp, especially in the head. Putting the probe in the radiator will allow the fan to operate only when really needed. If your fan is not pulling enough cfm, though, then maybe you are correct and running it on all the time is best. In that case, forget the temp sensor/probe and run a toggle switch to the dash like a race car. You can then turn it on and off whenver you want based on what your temp gauge reads or just leave it on all the time.