HEATED SEAT ELEMENT
DESCRIPTION
The heated seat element is the component which
produces the heat felt in the front seats. The heated
seat system includes four seat heating elements. Two
elements are located in each front seat, one for the
seat cushion (Fig. 7) and the other for the seat back.
These individual heating elements are electrically
connected in series with the Memory Heated Seat/
Mirror Module. With the elements electrically con-
nected in this way, if a break anywhere in the
heating element circuit occurs, neither the seat cush-
ion or seat back heating element will function. The
heating elements are made of carbon fiber, which
provides a strong and dependable design. Refer to
Heated Seat Element Diagnosing and Testing for
detailed diagnostic procedures.
A heated seat sensor is integral to the individual
heated seat cushion elements. The heated seat sensor
cannot be replaced separately. If a problem is found
with the sensor the complete heated seat element
must be replaced. On some models, this can also
include the leather trim cover. Refer to Heated Seat
Sensor in this section for more information.
Some LH models have the heating elements stuck
to the seat cushion foam, while others have the ele-
ment permanently sewn into the seat cushion/back
leather trim covers. The heated seat elements and
temperature sensor cannot be adjusted or repaired
and, if faulty or damaged, the heated seat element
must be replaced.
OPERATION
The heated seat elements resist the flow of electri-
cal current. When battery current is passed through
the elements, the energy lost by the resistance of the
elements is released in the form of heat. The heated
seat temperature sensor is a NTC thermistor. When
the temperature of the seat cushion cover rises, the
resistance of the sensor decreases. The Memory
Heated Seat/Mirror Module supplies five volts to one
side of each sensor, and monitors the voltage drop
through the sensor on a signal/return circuit. The
Memory Heated Seat/Mirror Module uses this tem-
perature sensor input to monitor the temperature of
the seat, and regulates the current flow to the heated
seat elements accordingly.
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT
The following procedure will check the heated seat
elements as well as the related seat wire harness
and connectors. This way, if there is a fault with the
seat wire harness leading to the heated seat element
or connector(s) it can also be detected. Without
checking the heated seat element in this way, a fault
with the seat wire harness or connector(s) would not
be detected.
The heated seat elements in the seat cushion and
seat back are connected in series with each other and
the controlling module. With the system wired this
way, if a open or fault occurs the entire seat may not
heat, even though the open may only be in the seat
cushion element.
Over time, the heated seat element may degrade
and require replacement. The memory heated seat/
mirror module should detect a fault before the ele-
ment completely fails. Always use the appropriate
scan tool (DRB III
t) to check the module for any
stored fault codes prior to any testing of the individ-
ual heated seat components.
NOTE: When checking heated seat elements for
continuity, be certain to move the heating element
being checked. Moving the element, such as sitting
in the seat will eliminate the possibility of an inter-
mittent open in the element which would only be
evident if the element was in a certain position.
Failure to check the element in various positions
could result in an incomplete test.
Fig. 7 Heated Seat Element – Typical
1 - SEAT BACK WIRE HARNESS
2 - HEATED SEAT WIRE HARNESS CONNECTOR
3 - HEATED SEAT CUSHION ELEMENT
LH
HEATED SEAT SYSTEM
8G - 15