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8N - 2
ELECTRICALLY HEATED SYSTEMS
DESCRIPTION AND OPERATION
HEATED SEAT SWITCH
The heated seat switch is located in the floor con-
sole. The two six-position rotating-type switches, one
switch for each front seat, provide a voltage signal to
their
respective
Heated
(HSCM). Each switch has 0 – 6 positions so that both
the driver and front seat passenger can select a pre-
ferred seat heating mode.
There are three Light-Emitting Diodes (LED's) in
the heated seat switch. The first LED illuminates the
heated seat symbol on the switch any time the igni-
tion switch is turned on and the remaining LED's
illuminate the numbers on each switch to indicate
the system is turned on.The heated seat switch and
their LED's cannot be repaired. If faulty, the switch
unit must be replaced.
HEATED SEAT CONTROL MODULE
The Heated Seat Control Module (HSCM) is an
electronic thermostatic module designed to operate
the electric seat heater elements. Two modules are
used in the vehicle, one for each front seat. The
HSCM for each seat is mounted to the seat cushion
frame.
Inputs to the module include the resistor heated
seat switch, the seat cushion temperature sensors, an
ignition-switched battery feed, an unswitched battery
feed, and a ground. The only HSCM output is the
feed for the seat heating elements.
The HSCM cannot be repaired and, if faulty, must
be replaced.
HEATED SEAT ELEMENTS AND SENSOR
Three seat heating elements are used in each front
seat, two for the seat cushion and one for the seat
back. The three elements for each seat are connected
in series with the HSCM.
The temperature sensor is a negative temperature
coefficient thermistor. One temperature sensor is
used for each seat, and it is integrated into 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, the
affected seat cover assembly must be replaced. Refer
to Group 23 - Body Components for the seat cover
service procedures.
Seat
Control
Module
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.
Before testing the individual components in the
heated seat system check the following:
• If the heated seat switch LED's do not light with
the ignition switch in the On position and the heated
seat switch in 1– 6 positions, check the 10 amp fuse
in cavity #11 located in the junction block and the 20
amp fuse in cavity # 8 of the Power Distribution Cen-
ter. If the fuse is OK, test the heated seat switch as
described in this group.
• If the heated seat switch LED's light, but the heat-
ing elements do not heat, check the 20 amp MAXI fuse
located in the Power Distribution Center in the engine
compartment. If the fuse is OK, remove the front seat
and test the heating elements for continuity.
HEATED SEAT SWITCH
For circuit descriptions and diagrams, refer to
8W-63 - Power Seat With Heated Seats in Group 8W
- Wiring Diagrams.
(1) Remove the heated seat switch as described in
this group and inspect connector for damage. Unplug
the 7-way connector from the switch and check the
pin terminals for ignition voltage and ground.
(2) Check
the
drivers
between pin terminals PB and 86B. Resistance
should vary as the switch is rotated (Fig. 1). If OK,
go to Step 3. If not OK, replace the heated seat
switch.
(3) Check the passenger switch for resistance
between pin terminals PF and 86F. Resistance should
vary as the switch is rotated (Fig. 1). If OK, test
heated seat control module as described in this
group. If not OK, replace the heated seat switch.
Fig. 1 Heated Seat Switch
JA
switch
for
resistance
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