Jeep XJ. Manual — part 137
HEATED SEAT SYSTEM
TABLE OF CONTENTS
page
page
GENERAL INFORMATION
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . 8
DESCRIPTION AND OPERATION
HEATED SEAT SWITCH. . . . . . . . . . . . . . . . . . . . . 8
SEAT HEAT INTERFACE MODULE. . . . . . . . . . . . . 9
HEATED SEAT RELAY . . . . . . . . . . . . . . . . . . . . . . 9
HEATED SEAT ELEMENT and SENSOR . . . . . . . . 9
DIAGNOSIS AND TESTING
HEATED SEAT SYSTEM . . . . . . . . . . . . . . . . . . . . 9
HEATED SEAT SWITCH . . . . . . . . . . . . . . . . . . . . 10
HEATED SEAT ELEMENT and SENSOR. . . . . . . . 11
HEATED SEAT RELAY . . . . . . . . . . . . . . . . . . . . . 11
SEAT HEAT INTERFACE MODULE. . . . . . . . . . . . 12
REMOVAL AND INSTALLATION
GENERAL INFORMATION
INTRODUCTION
Individually controlled electrically heated front
seats are available factory-installed optional equip-
ment on this model. The seat heaters will only oper-
ate when the ignition switch is in the ON position,
and the surface temperature at the front seat heating
element sensors is below the designed temperature
set points of the system. The heated seat system will
not operate in ambient temperatures greater than
about 32° C (90° F).
There are separate momentary, tactile, two-direc-
tional rocker switches located in the center console
with center NEUTRAL, HI and LO positions for each
front seat. Depressing the rocker switch to its
momentary HI or LO position signals the Seat Heat
Interface Module (SHIM) to power the selected
heated seat and maintain the requested temperature
setting (HI or LO). Each switch has a HI and LO
Light-Emitting Diode (LED) which, via the SHIM,
illuminates to give a visual indication that the sys-
tem is in the HI or LO mode. The LO heat set point
is about 32° C (90° F), and the HI heat set point is
about 38° C (100° F). The system shall be deactivated
whenever the same set position is depressed a second
time and shall change states directly when switching
from HI to LO or vice versa. The system shall be
deactivated whenever the ignition switch is placed in
the off position. When the ignition switch is placed
back in the run position, the heated seat system
shall remain deactivated until a momentary switch is
depressed. When a seat heater is turned on, a sensor
located near the seat cushion electric heater element
provides the SHIM with input indicating the surface
temperature of the seat cushion. If the surface tem-
perature input is below the temperature set point of
the SHIM for the selected temperature setting, an
N-FET Transistor within the SHIM energizes the
heating elements in the seat cushion and back. When
the sensor input indicates the correct temperature
set point has been achieved, the SHIM de-energizes
the N-FET. The SHIM will continue to cycle the
N-FET as needed to maintain the temperature set
point.
The SHIM will automatically turn off the heating
elements if it detects a short or an open in the heat-
ing element or a sensor out of range. These condi-
tions will also cause the SHIM to notify the occupant
of the failure via flashing the heated seat switch
LED’s as discussed later.
Switched battery power to the SHIM is supplied by
the heated seat relay mounted to the seat cushion
frame with the SHIM under the right front seat. The
battery feed is protected by a circuit breaker located
in the junction block.
Following are general descriptions of the major
components in the heated seat system. Refer to
8W-63 - Power Seat With Heated Seats in Group 8W
- Wiring Diagrams for complete circuit descriptions
and diagrams.
DESCRIPTION AND OPERATION
HEATED SEAT SWITCH
The heated seat switch assembly is located on the
center console where the ashtray is normally located
(Fig. 1). The two momentary, two-directional rocker
switches, one switch for each front seat, provide a
resistor-multiplexed signal to the Seat Heat Interface
Module (SHIM). Each switch has center NEUTRAL,
and momentary LO and HI positions so that both the
driver and the front seat passenger can select a pre-
ferred seat heating mode.
Each switch has two telltales (LED’s) which indi-
cate the mode of the heater of the respective seat.
8N - 8
ELECTRICALLY HEATED SYSTEMS
XJ
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)
SEAT HEAT INTERFACE MODULE DIAGNOSTIC ROUTINES
FAILURE MODE
SWITCH “HI” TELLTALE
SWITCH “LO” TELLTALE
Shorted Heating Element
Flashing
Flashing
Open Heating Element
Flashing
Off
NTC Value Out of Range
Off
Flashing
Before testing the individual components in the
heated seat system, check the following:
• If the heated seat switch backlighting does not
illuminate with the ignition switch in the ON posi-
tion, check the fuse in the junction block. If the fuse
is OK, see Heated Seat Switch Backlighting in the
Diagnosis and Testing section of this group. If not
OK, repair the shorted circuit or component as
required and replace the faulty fuse.
• If the heated seat switch telltales do not illumi-
nate with the ignition switch in the ON position, but
the heating elements do heat, see Heated Seat
Switch Telltales in the Diagnosis and Testing section
of this group.
• If the heated seat switch backlighting illumi-
nates with the ignition switch in the ON position,
but the heating elements do not heat and the tell-
tales do not illuminate, check the circuit breaker in
the junction block. If the circuit breaker is OK, see
Heated Seat Switch Multiplexed Resistances in the
Diagnosis and Testing section of this group. If not
OK, replace the faulty circuit breaker.
• If the heated seat switch backlighting illumi-
nates and the telltales illuminate, but the heating
elements do not heat; see Heated Seat Element in
the Diagnosis and Testing section of this group.
HEATED SEAT SWITCH
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.
BACKLIGHTING
(1) Disconnect and isolate the battery negative
cable
(2) Remove the heated seat switch assembly from
the center console. Remove the connector from the
suspect switch. Check for continuity between the
ground circuit cavity of the 6-way heated seat switch
wire harness connector and a good ground. There
should be continuity. If OK, go to Step 3. If not OK,
repair the open circuit as required.
(3) Connect the battery negative cable. Turn the
ignition switch to the ON position. Check for battery
voltage at the fused ignition switch output circuit
cavity of the 6-way heated seat switch wire harness
connector. If OK, turn the ignition switch to the OFF
position, disconnect and isolate the battery negative
cable, and replace the heated seat switch. If not OK,
repair the open circuit as required.
TELLTALES
(1) Replace the heated seat switch with a known
good unit and test the operation of the switch tell-
tales. If OK, discard the faulty heated seat switch. If
not OK, see Seat Heat Interface Module in the Diag-
nosis and Testing section of this group.
MULTIPLEXED RESISTANCES
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the heated seat switch assembly from
the center console. Remove the connector from the
suspect switch.
(3) With the suspect heated seat switch in the
NEUTRAL position, using an ohmmeter, measure the
resistance between the fused ignition switch output
circuit terminal and the heated seat switch output
circuit terminal in the 6-way connector receptacle on
the back of the switch. The resistance reading should
be about 2.2. Kohms. If OK, go to Step 4. If not OK,
replace the faulty switch.
(4) Hold the suspect heated seat switch in the LO
position. Using an ohmmeter, check the resistance
between the fused ignition switch output circuit ter-
minal and the heated seat switch output circuit ter-
minal in the 6-way connector receptacle on the back
of the switch. The resistance reading should be about
414 Ohms. If OK, go to Step 5. If not OK, replace the
faulty switch.
(5) Hold the suspect heated seat switch in the HI
position. Using an ohmmeter, check the resistance
between the fused ignition switch output circuit ter-
minal and the heated seat switch output circuit ter-
minal in the 6-way connector receptacle on the back
8N - 10
ELECTRICALLY HEATED SYSTEMS
XJ
DIAGNOSIS AND TESTING (Continued)
of the switch. The resistance reading should be about
32.5 Ohms. If OK, see Heated Seat Relay in the
Diagnosis and Testing section of this group. If not
OK, replace the faulty switch.
HEATED SEAT ELEMENT and SENSOR
The wire harness connectors for the seat cushion
and seat back heating elements are located under the
seat, near the rear edge of the seat cushion frame.
For circuit descriptions and diagrams, refer to 8W -
63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.
SEAT CUSHION
(1) Disconnect and isolate the battery negative
cable. Unplug the 4-way heated seat cushion wire
harness connector.
(2) Check for continuity between the two heated
seat element circuit cavities of the seat cushion cover
half of the heated seat cushion wire harness connec-
tor. There should be continuity. If OK, go to Step 3. If
not OK, replace the faulty seat cushion cover.
(3) Check for continuity between one of the heated
seat element circuit cavities of the seat cushion cover
half of the heated seat cushion wire harness connec-
tor and the seat cushion frame. There should be no
continuity. If OK, see Seat Back in the Diagnosis and
Testing section of this group. If not OK, replace the
faulty seat cushion cover.
SEAT BACK
(1) Disconnect and isolate the battery negative
cable. Unplug the 2-way heated seat back wire har-
ness connector.
(2) Check for continuity between the heated seat
element circuit cavity and the ground circuit cavity of
the seat back cover half of the heated seat back wire
harness connector. There should be continuity. If OK,
go to Step 3. If not OK, replace the faulty seat back
cover.
(3) Check for continuity between the heated seat
element circuit cavity of the seat back cover half of
the heated seat back wire harness connector and the
seat back frame. There should be no continuity. If
OK, see Heated Seat Sensor in the Diagnosis and
Testing section of this group. If not OK, replace the
faulty seat back cover.
HEATED SEAT SENSOR
The wire harness connector for the seat cushion
heating element and sensor are located under the
seat, near the rear edge of the seat cushion frame.
For circuit descriptions and diagrams, refer to 8W -
63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.
(1) Disconnect and isolate the battery negative
cable. Unplug the 4-way heated seat cushion wire
harness connector.
(2) Using
an
ohmmeter,
check
the
resistance
between the heated seat sensor input circuit cavity
and the heated seat sensor feed circuit cavity of the
seat cushion cover half of the heated seat cushion
wire harness connector. The sensor resistance should
be between 1 Kohm and 200 Kohms. If OK, see
Heated Seat Relay in the Diagnosis and Testing sec-
tion of this group. If not OK, replace the faulty seat
cushion cover.
HEATED SEAT RELAY
For circuit descriptions and diagrams, refer to 8W -
63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.
(1) Disconnect and isolate the battery negative
cable. Unplug the 8-way heated seat relay connector.
(2) Check for continuity between the ground cir-
cuit cavity of the 8-way heated seat relay wire har-
ness connector and a good ground. There should be
continuity. If OK, go to Step 3. If not OK, repair the
open circuit as required.
(3) Connect the battery negative cable. Check for
battery voltage at the battery feed circuit cavity (pin
8) of the 8-way heated seat relay wire harness con-
nector. If OK, go to Step 4. If not OK, repair the open
circuit as required.
(4) Turn the ignition switch to the ON position.
Check for battery voltage at the fused ignition switch
output circuit cavity of the 8-way heated seat relay
wire harness connector. If OK, turn the ignition
switch to the OFF position, disconnect and isolate
the battery negative cable, and go to Step 5. If not
OK, repair the open circuit as required.
(5) Unplug the 14-way seat heat interface module
(SHIM) connector. Check for continuity between the
two switched battery feed cavities of the 14-way
SHIM wire harness connector and the switched bat-
tery feed cavity of the 8-way heated seat relay wire
harness connector. If OK, reconnect the heated seat
relay wire harness connector, and go to Step 6. If not
OK, repair the open circuit as required.
(6) Connect the battery negative cable. Turn the
ignition switch to the ON position. Check for battery
voltage at the switched battery feed cavities of the
14-way SHIM wire harness connector. If OK, turn
the ignition switch to the OFF position, disconnect
and isolate the battery negative cable, and see Seat
Heat Interface Module in the diagnosis and testing
section of this group. If not OK, replace the heated
seat relay.
XJ
ELECTRICALLY HEATED SYSTEMS
8N - 11
DIAGNOSIS AND TESTING (Continued)
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст