Seat Temperature Sensor: Description and Operation

Fig.5 Heated Seat Cushion Trim Cover - Typical:

The heated seat sensors are Negative Thermal Coefficient (NTC) thermistors. One temperature sensor is used for each front seat, and it is located in the center insert area of the seat cushion cover. The heated seat sensors and their pigtail wires are captured between the seat cushion trim cover and the foam rubber backing on the underside of the cover, like the heated seat elements. Short pigtail wires are soldered to each end of the sensor and they share a 4-way connector with the pigtail wires from the heated seat cushion elements.

The heated seat sensors are integral to their respective seat cushion cover assemblies, which are serviced individually. The heated seat sensors cannot be adjusted or repaired; however, their pigtail wires and connectors can be repaired. Refer to the appropriate wiring information for the proper wire and connector repair procedures. If a heated seat sensor is damaged or faulty, the affected seat cushion trim cover unit must be replaced. Refer to the appropriate service information for the proper seat trim cover service procedures.

The resistance of the heated seat sensor increases and decreases as the surface temperature of the seat cushion cover changes. A single output of the heated seat module (Seat Heat Interface Module or SHIM) supplies each sensor with a reference voltage through the sensor feed circuit. The SHIM then detects the sensor resistance by monitoring the return voltage on separate return inputs through the driver and passenger heat sense input circuits. The SHIM uses the heated seat sensor resistance (seat cushion surface temperature) input to determine when to energize or de-energize the N-FET so that the heated seat element grids are cycled ON or OFF as needed to maintain the selected temperature set point.