Negative Temperature Coefficient Sensors
Negative Temperature Coefficient (NTC) sensors allow voltage to flow more freely when hot. The sensor in the illustration is an example of an NTC sensor.
It's a thermistor, a variable resistor that changes resistance with temperature. Notice it has two wires that lead to the controller; one is its 5-volt reference signal, and the other is ground.
The controller uses this signal to make output decisions based on seat temperature as resistance changes. For example, if the seat is too hot, the controller slows or stops the flow of electricity through the elements. In addition, the module uses the signal for safety and for regulating temperatures for HI and LOW settings.