Hi, does anyone know if a bad ECT sensor can override the fan switch? It's known the ECU has a wire labeled FANC (pin A12) but I'm told is not used on stock ECUs. My fan switch is supposed to turn on at 93 deg C and off at 88 deg C. The fan turns on briefly at 93 but turns off shortly when stationary (around 5 sec) and clearly above 88 C (tested with a thermometer pointing to the upper rad hose close to the switch). I have tested with two different fan switches (one known good and other brand new).

 

Fan switch seems fine as long as your engine is not overheating,