Absolute crap. The electric fans are turned on in series (so they run slowly) by the HEVAC as they are there to cool the AC condenser. If the engine gets really hot, the engine ECU will bring them on in parallel so they run at high speed.Yes there is a temp sensor on the bottom of the radiator. It measures the coolant temp returning to the engine. It's used to turn on the electric fans. A separate sensor is especially needed for variable speed fans.