Montana SV6 V6-3.9L (2007)
Seat Heater: Description and Operation
Heated Seats Description and Operation
The driver and front passenger heated seats each consist of the following components.
* Heated seat switch
* HVAC control module
* Body control module (BCM)
* Heated seat relay - Driver
* Heated seat relay - Passenger
* Seat cushion heater element
* Seat back heater element
* Temperature sensor
* HTD/SEATS fuse
Power and Ground
Battery positive voltage is supplied at all times to both front heated seat relays from the HTD SEATS fuse located in the instrument panel (I/P) fuse
panel. Both relays are grounded through the relay ground circuits and G301.
Heated Seat Operation
The driver and passenger heated seats are controlled by separate heated seat switches. Both switches are located in the HVAC control module. When a
heated seat switch is pressed, the HVAC control module sends a class 2 message to the body control module (BCM) indicating the heated seat command.
In response to this signal, the BCM applies battery positive voltage through the heated seat relay control circuit energizing the relay. The relay closes its
switch contacts applying battery positive voltage through the element supply voltage circuit to the seat heating elements. The BCM then sends a class 2
message back to the HVAC control module to illuminate the appropriate temperature indicator.
Temperature Regulation
When the ignition is turned to the ON position, the heated seats will initialize in the OFF state. With each activation of the heated seat switch, the body
control module (BCM) will cycle temperature setting in the following manner: HIGH, LOW, and OFF.
The heated seat system is designed in order to warm the seat cushion and seat back to approximately 42°C (107.6°F) when in the high heat position,
and 37°C (98.6°F) when in the low heat position. The BCM monitors the seat temperature through the temperature sensor signal circuit and the
temperature sensor (thermistor) that is located in the seat cushion. The temperature sensor is a variable resistor, its resistance changes as the temperature
of the seat changes. When the temperature sensor resistance indicates to the BCM that the seat has reached the desired temperature, the module removes
battery voltage from the heated seat relay control circuit de-energizing the relay. The relay then opens it's switch contacts removing battery voltage from
the heated seat element supply voltage circuit and the seat heating elements. The module will then cycle the relay control circuit ON and OFF in order to
maintain the desired temperature.
Load Management
During Heated Seats Load Shed Level 1, the body control module (BCM) will cycle the heated seat operation 16 seconds ON and 4 seconds OFF.
During Heated Seats Load Shed Level 2, the BCM will deactivate the heated seat operation, and signal the climate control panel (CCP) turn OFF the
appropriate heated seat temperature indicators.
