Grand Cherokee 2WD Limited V8-4.7L (2002)
Fig.5 Heating Element Installed - Typical
HEATED SEAT ELEMENT
The heated seat system includes two seat heating elements in each front seat, one for the seat cushion and the other for the seat back. One type of
heated seat element is offered. All models use two resistor wire heating elements for each seat that are connected in series with the Heated Seat
Module (HSM).
The seat heating elements are glued to the seat and seat back cushions. The heated seat elements can be replaced if faulty or damaged, service
replacement seat or seat back elements are available. Refer to the procedure in this section for detailed instructions.
The heated seat elements resist the flow of electrical current. When battery current is passed through the elements, the energy lost by the resistance
of the elements to the current flow is released in the form of heat. The temperature sensor is a NTC thermistor. When the temperature of the seat
cushion cover rises, the resistance of the sensor decreases. The HSM or MHSM supplies a five-volt current to one side of each sensor, and
monitors the voltage drop through the sensor on a return circuit. The MSM or MHSM uses this temperature sensor input to monitor the
temperature of the seat, and regulates the current flow to the seat heating elements accordingly.
HEATED SEAT SENSOR
The heated seat temperature sensor is a Negative Temperature Coefficient (NTC) thermistor. One temperature sensor is used for each seat. This
temperature sensor is located in the seat cushion heating element on all models.
The heated seat temperature sensor cannot be repaired or adjusted and must be replaced if defective. The heated seat cushion element must be
replaced if the temperature sensor is defective. Refer to the procedure in this section.
