HEATED SEATS
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
HEATED SEAT SYSTEM ....................6
HEATED SEAT SWITCH.....................6
MEMORY HEATED SEAT/MIRROR MODULE
(MHSMM) ..............................7
HEATED SEAT ELEMENT AND SENSOR........7
DIAGNOSIS AND TESTING
HEATED SEAT SYSTEM ....................7
HEATED SEAT SWITCH.....................8
MEMORY HEATED SEAT / MIRROR MODULE
(MHSMM) ..............................8
HEATED SEAT ELEMENT ...................8
HEATED SEAT SENSOR ....................8
REMOVAL AND INSTALLATION
HEATED SEAT SWITCH.....................9
MEMORY HEATED SEAT / MIRROR MODULE
(MHSMM) ..............................9
DESCRIPTION AND OPERATION
HEATED SEAT SYSTEM
DESCRIPTION
Heated seats only available with leather and mem-
ory. The seat heaters are controlled by the Memory
Heated Seat and Mirror Module (MHSMM). The
heaters will only operate when the ignition switch is
in the ON position, and the surface temperature at
the from seat heating element sensors is below the
designed temperature set points of the system.
OPERATION
The heater switch is a three position (HI, LO, and
neutral position OFF) momentary rocker switch.
Green LED’s illuminate the switch for night visibil-
ity. Amber LED’s are located in the switch adjacent
to the HI and LO graphics, which indicate the
selected operating mode of the seat heater, The LO
heat position set point is about 98° F and the HI set
point is about 107° F.
The heaters are solid high side driven, and are
controlled by an NTC circuit. When either HI or LO
is activated, the temperature in the seat rises the
Negative Temperature Coefficient (NTC) resistance
decreases, and the voltage reading detected by the
MHSMM increases. The seat heater output is deacti-
vated once the voltage reading reaches its upper
threshold for either of the settings, HI or LO.
As the temperature decreases the voltage reading
decreases until the lower threshold is reached for
either setting, HI or LO. At this point the seat heat
output is activated once again. This cycle repeats
itself as long as the seat heat request remains on.
The thresholds for high and low settings are pre-pro-
grammed into the MHSMM.
The system will automatically turn off when the
ignition is turned to the OFF position. For complete
circuit descriptions and diagrams, refer to Group 8W,
Wiring Diagrams.
HEATED SEAT SWITCH
DESCRIPTION
The heated seat switch is located in the outboard
cushion side shield of the driver and passenger seats.
OPERATION
The switch is a three position (HI, LO, and OFF)
momentary rocker switch. Green LED’s illuminate
the switch for night visibility. Amber LED’s are
located in the switch adjacent to the HI and LO
graphics, which indicate whether low or high has
been selected. The heated seat switches and their
LED’s are not repairable. If either the switch or LED
is faulty, the switch will have to be replaced.
Fig. 1 Memory and Heated Seat Switch Location
1 – HEATED SEAT SWITCH
2 – POWER SEAT SWITCH
3 – SEAT CUSHION SIDE SHIELD
4 – MEMORY SELECTOR SWITCH
8N - 6 ELECTRICALLY HEATED SYSTEMS LH
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