Jeep Cherokee 2000 Service Manual - page 506
The switches also have LED’s which provide back-
lighting when the ignition switch is in the ON posi-
tion. The LED’s cannot be repaired. If the LED is
faulty, the individual switch must be replaced.
SEAT HEAT INTERFACE MODULE
The Seat Heat Interface Module (SHIM) is an elec-
tronic microprocessor controlled device designed to
operate the electric seat heater elements. The SHIM
is located under the right front seat cushion. Inputs
to the module include the console mounted resistor
multiplexed switch signals, seat cushion temperature
sensors, a relay-switched battery feed, and a ground.
The SHIM outputs are the feed for the seat heating
elements and sensors, and the switch telltale circuits.
The SHIM cannot be repaired and, if faulty or dam-
aged, it must be replaced.
HEATED SEAT RELAY
The heated seat relay is located under the right
front seat cushion near the SHIM. Ignition and bat-
tery power is fed to the relay, which then provides a
switched battery feed to the SHIM. The heated seat
relay cannot be repaired and, if faulty or damaged, it
must be replaced.
HEATED SEAT ELEMENT and SENSOR
Two heated seat heating elements are used in each
front seat, one for the seat cushion and the other for
the seat back. The two elements for each seat are
connected in series with the SHIM.
The temperature sensor is a Negative Temperature
Coefficient (NTC) thermistor. One temperature sen-
sor is used for each seat, and it is integral to the seat
cushion heating element.
The heating elements are sewn into the seat cush-
ion cover and seat back cover assemblies, which are
serviced individually. The heating elements and tem-
perature sensor cannot be repaired and, if faulty or
damaged, the affected seat cover assembly must be
replaced. Refer to Group 23 - Body for the seat cush-
ion cover and seat back cover Removal and Installa-
tion.
DIAGNOSIS AND TESTING
HEATED SEAT SYSTEM
For circuit descriptions and diagrams, refer to 8W -
63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,
REFER
TO
GROUP
8M
-
PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING
WHEEL,
STEERING
COLUMN,
OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
The heated seat system is capable of performing
some self-diagnostics. The following table depicts the
various failure modes which will be reported to the
occupant via flashing the momentary switch telltales.
The switch telltales will flash on the driver’s switch
if the failure exists in the driver’s seat portion of the
system, similarly with the passenger’s switch. The
telltale will illuminate for approximately a
1
⁄
2
second
on,
1
⁄
2
second off pulse for a duration of one minute.
This process will repeat every time the system is ini-
tiated via the switches until the problem has been
corrected.
Fig. 1 Heated Seat Switch Location
1 – ASH RECEIVER
2 – HEATED SEAT SWITCHES & BEZEL
3 – WIRE HARNESS CONNECTORS
4 – FLOOR CONSOLE
XJ
ELECTRICALLY HEATED SYSTEMS
8N - 9
DESCRIPTION AND OPERATION (Continued)