If you are going to replace the fan sensor you may want to replace the coolant thermostat as well.
These two devices work together to maintain proper engine temperature.
The coolant thermostat will be rated at a temperature slightly lower than the fan sensor.
For example the coolant thermostat will control the coolant temperature at approx. 190* by controlling the amount of coolant that flows through the engine/radiator.
If coolant temperature rises to 195* the fan sensor will then run the fan thus cooling the system down 190*.