Caravan FWD V6-3.3L VIN R (2001)
The seat heating elements are sewn into the seat cushion cover trim and seat back cover trim units. The heated seat elements and the temperature
sensor cannot be adjusted or repaired and, if faulty or damaged, the seat cushion or seat back assembly must be replaced. Refer to Seat Cushion or
Seat Back in the Removal and Installation for the seat cushion and seat back service procedures.
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, and is
integrated into the seat cushion heating element.
Fig.1 Heated Seat Switches
PASSENGER HEATED SEAT SWITCH
The heated seat switches are mounted in the instrument panel center bezel. The two three-position rocker-type switches, one switch for each front
seat, are incorporated into one large switch assembly that also includes the hazzard, rear window wiper and washer switches. The heated seat
switches provide a resistor multiplexed signal to the Body Control Module (BCM) through separate hard wired circuits. Each switch has an OFF,
Low, and High position so that both the driver and the front seat passenger can select a preferred seat heating mode. Each switch has two
Light-Emitting Diodes (LED) which light to indicate that the heater for the seat is turned ON.
The heated seat switches and their LEDs cannot be repaired. If either switch or LED is faulty or damaged, the entire switch assembly must be
replaced.
There are three positions that can be selected with each of the heated seat switches: OFF, Low, or High. When the left side of the. switch rocker is
fully depressed, the Low position is selected and the high position LED indicator illuminates. When the right side of the switch rocker is fully
depressed, the High position is selected and the low position LED indicator illuminates. when the switch rocker is moved to its neutral position
(middle), OFF is selected and both LED indicators are extinguished.
Both switches provide separate resistor multiplexed hard wire inputs to the BCM to indicate the selected switch position. The BCM monitors the
switch inputs and sends heated seat switch status messages to the Heated Seat Module (HSM) or the Memory Heated Seat Module (MHSM) over
the Programmable Communications Interface (PCI) data bus. The HSM or MHSM responds to the heated seat switch status messages by
controlling the output to the seat heater elements of the selected seat. The Low heat position set point is about 36 °C (97 °F), and the High heat
position set point is about 41 °C (105 °F).
