Grand Cherokee 4WD V8-4.7L VIN N (2000)
Seat Heater Switch: Description and Operation
The heated seat switches are mounted in the center lower bezel, which is located near the bottom of the instrument panel center stack. The two
three-position rocker-type switches, one switch for each front seat, 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), one each for the Low position and the High position, which light to indicate that
the heater for the seat that the switch controls is turned on. Each switch is also back lit by a replaceable incandescent bulb.
The heated seat switches and their LEDs cannot be repaired. If either switch or LED is faulty or damaged, the entire switch unit must be replaced. The
incandescent switch illumination bulb and bulb holder units are available for service replacement.
There are three positions that can be selected with each of the heated seat switches: Off, Low, or High. When the top of the switch rocker is fully
depressed, the High position is selected and the high position LED indicator illuminates. When the bottom of the switch rocker is fully depressed, the
Low position is selected and the low position LED indicator illuminates. When the switch rocker is moved to its neutral position, 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).