Thermo Fan Switch (T.F.S)

The thermo fan switch is also a thermistor.

This one in particular is NTC.

It has semi-conductive properties which causes its resistance to decrease as the temperature increases; as explained in the ECT post.

Suspend the thermo fan switch in a container of water and record the results.

As you can see in the graph, the resistance is at its highest when the TFS is cold, and gradually the resistance decreases as the temperature gets hotter.

Note at approximately 98 degrees Celsius, the resistance is so low that it goes "OL".

When this occurs, the semi-conductive materials in the thermistor are allowing more electricity to flow freely, so that there is no resistance.

Therefore, the circuit can be complete by electricity flowing freely without any resistive opposition. The switch is on, and it works fine.