Grand Cherokee 2WD V6-3.7L (2008)
Seat Heater Control Module: Description and Operation
Operation
OPERATION
FRONT SEAT HEATED SEAT SYSTEM OPERATION
The front heated seat system operates on battery current received through a 20 amp fuse in the Power Distribution Center (PDC). Fused ignition switch
output circuits are used, so that the systems will only operate when the ignition switch is in the ON position. The heated seat system will turn off
automatically whenever the ignition switch is turned to any position except On. If the ignition switch is turned to the OFF position while a heated seat is
on, the heated seat will remain off after the engine is restarted until a front seat heated seat switch is depressed again. This prevents the vehicles battery
from being drained by the heated seat system.
The heated seat switches for the front row seats are located in the lower instrument panel switch pod assembly. The lower switch pod assembly is
mounted in the lower portion of the instrument panel center stack. Amber Light Emitting Diodes (LEDs) in each switch indicate the level of heat in use:
Two LEDs are illuminated for high, one for low, and none for off. Pressing the switch once will select high-level heating. Pressing the switch a second
time will select low-level heating. Pressing the switch a third time will shut the heating elements off. The switch LEDs are controlled by the instrument
cluster.
A Heated Seat Module is used to control the heated seat system. The module is secured to a mounting bracket located under the right front seat. The
module responds to heated seat switch messages and ignition switch status inputs by controlling the 12v output to the seat heating elements through
integral solid-state relays.
When either of the front heated seat switches are depressed a resistance signal is sent to the ElectroMechanical Instrument Cluster (EMIC) (also known
as the Cab Compartment Node/CCN). The instrument cluster receives this message via the Local Interconnect Network (LIN) data bus. The instrument
cluster then sends a message via the Controller Area Network (CAN) data bus to the heated seat module, signaling the module to energize the heating
element for the selected seat.
The heated seat module energizes an integral solid-state relay, which supplies battery current to the heating elements. Heated seats turn off after one hour
of continuous operation. If high-level heating is selected, the control system will remain at the high level for 30 minutes and then drop to the low level
for 30 minutes. Then it will turn off. At that time, the number of illuminated LEDs changes from two to one, indicating the change.
The module will automatically turn off the heating elements if it detects an OPEN or LOW short in the heating element circuit.
2ND ROW HEATED SEAT SYSTEM OPERATION
The 2nd row heated seat system operates on battery current received through a 20 amp fuse in the Power Distribution Center (PDC). Fused ignition
switch output circuits are used, so that the systems will only operate when the ignition switch is in the ON position. The heated seat system will turn off
automatically whenever the ignition switch is turned to any position except On. If the ignition switch is turned to the OFF position while a heated seat is
on, the heated seat will remain off after the engine is restarted until a front seat heated seat switch is depressed again. This prevents the vehicles battery
from being drained by the heated seat system.
The heated seat switches for the 2nd row seats are located in the rear center floor console. Amber Light Emitting Diodes (LEDs) in the top portion of
each switch indicate the level of heat in use: Two LEDs are illuminated for high, one for low, and none for off. Pressing the switch once will select
high-level heating. Pressing the switch a second time will select low-level heating. Pressing the switch a third time will shut the heating elements off.
The 2nd row heated seat system utilizes the same heated seat module as the front heated seat system. The module is secured to a mounting bracket
located under the right front seat. The module responds to heated seat switch messages and ignition switch status inputs by controlling the 12v output to
the seat heating elements through integral solid-state relays.
When either of the 2nd row heated seat switches are depressed a hardwired resistance signal is sent to the ElectroMechanical Instrument Cluster (EMIC)
(also known as the Cab Compartment Node/CCN). The instrument cluster then sends a message via the Controller Area Network (CAN) data bus
network to the heated seat module, signaling the module to energize the heating element for the selected seat. Light Emitting Diodes (LED) in each
switch indicate the level of heat in use. The switch LEDs are controlled by the instrument cluster.
The heated seat module energizes an integral solid-state relay, which supplies battery current to the heating elements. Heated seats turn off after one hour
of continuous operation. If high-level heating is selected, the control system will remain at the high level for 30 minutes and then drop to the low level
for 30 minutes. Then it will turn off. At that time, the number of illuminated LEDs changes from two to one, indicating the change.
The module will automatically turn off the heating elements if it detects an OPEN or LOW short in the heating element circuit.
