Avalanche 4WD V8-5.3L (2011)
heated cooled seat modes to the CCSM.
Modes of Operation
There are 3 modes available for climate control seat system operation, heated seat, cool seat, and back only heat operation. When a heat or cool seat
mode signal request is received, the CCSM will activate both the seat cushion and seat back ventilation modules. When the seat BACK ONLY mode
button is pressed once, the CCSM will deactivate the seat cushion ventilation module and leave the seat back ventilation module ON. Press the BACK
ONLY mode button a second time and the CCSM will re-activate the seat cushion ventilation module.
Heated and Cooled Seat Switches / HVAC Control Module
The heated and cooled seat system is controlled through 3 different switch inputs of the HVAC control module. When one of the switches is pressed, the
HVAC control module sends a serial data message to the MSM indicating the switch input. In response to this message, the MSM sends a pulse width
modulation (PWM) signal through the heated/cool seat mode signal circuit to the CCSM indicating the heated or cooled seat request. During heated or
cooled seat operation the HVAC control module displays the switch symbol of the active operating mode and the temperature level bars on the climate
control display determined by a serial data message from the MSM.
Temperature Sensors
As mentioned above in the heated/cool ventilation module description, the seat cushion and seat back temperature sensors are each packaged with a TED
and blower motor as an assembly. The seat temperature sensors are thermistors which are attached directly to the fins of each TED. The CCSM supplies
a 5 V reference voltage through the temperature sensor signal circuit and ground through the temperature sensor low reference circuit to the respective
seat cushion and seat back temperature sensors. As the temperature of the TED changes, the resistance of the thermistor varies changing the feedback
voltage of the temperature sensor signal circuit. This voltage varies from 0.5 - 4 V. The CCSM monitors this voltage signal to determine the fin
temperature so that it can adjust and maintain the seat temperature to the selected switch input.
Blower Motors
Also, as mentioned above in the heated/cool ventilation module description, the seat cushion and seat back blower motors are each packaged with a TED
and temperature sensor as an assembly. Each blower motor contains logic that will allow for the blower to operate only when the ignition is in the ON
position. When the ignition is ON and the CCSM is powered up, the module supplies battery positive voltage through the blower supply voltage circuit
to the logic of the blower motors. When the heated/cool seat switch is pressed, the CCSM applies a pre-determined voltage through the blower speed
control circuits to the blower motors. The module also supplies each blower motor with a ground path through the blower low reference circuits.
With the climate control seat system, the speed of the blower motor is not related directly to the High, Med, or Low input from the heated/cool seat
switch. The speed of the blower motor is related directly to TED temperature as described below in heated and cooled seat operation.
Heated Seat Operation
When the heated seat switch is pressed for High Heat, the CCSM will transition to the HEAT state. In the heat state, the CCSM applies a pre-determined
voltage through the ventilation module heat control circuits to the heat side of the TEDs, while providing a ground through the ventilation module cool
control circuit to the cool side of the TEDs. A pre-determined voltage is also applied to the blower motors. The CCSM uses the following sequence
beginning with the Heat SoftStart Mode to achieve the set point temperature before it can enter the Control Heat Mode. If the seat temperature is already
above the Temperature Set Point, the CCSM will skip the Heat SoftStart Mode and proceed to the Control Heat Mode.
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Heat SoftStart Mode - While in transition to the heat mode, the CCSM will initiate the SoftStart Mode. The intent of the Heat SoftStart Mode is
for the module to bring the ventilation module fin temperature up to the pre-determined Temperature Set Point of the Max Heat Mode. The
module does this by setting the blower motor speed control to a pre-determined voltage while ramping up the ventilation module voltage from 0
volts to the maximum voltage, not to exceed 5 seconds, at which point the system transitions to Max Heat Mode. The Heat SoftStart Mode will
only be attempted once per ignition cycle.
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Max Heat Mode - Upon completion of the Heat SoftStart Mode, the CCSM will initiate Max Heat Mode. The intent of the MAX Heat Mode is to
maintain the fin temperature to the pre-determined Temperature Set Point in order for the CCSM to go into the Control Heat Mode. The CCSM
does this by maintaining the TED at the maximum voltage while maintaining the minimum required airflow across the fins. After max heat
duration has been reached, or upon achieving the pre-determined Temperature Set Point, the system transitions to the Control Heat Mode.
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Control Heat Mode - At the completion of Max Heat Mode, the CCSM will initiate Control Heat Mode. The intent of the Control Heat Mode is to
maintain the desired fin temperature or the set point temperature. The CCSM does this in two ways; first by adjusting the voltage supply to the
blower motor to control blower motor speed, then secondly by controlling the voltage supplied to the TED. The CCSM updates these voltages
once every second. Increasing the blower motor speed will decrease the fin temperature. If the maximum blower motor speed is achieved and the
fin temperature is still above the set point of high heat, the CCSM will then begin to control the TED voltage to achieve Temperature Set Point.
Decreasing the TED voltage decreases the fin temperature. If the CCSM is trying to raise the fin temperature to set point by using TED voltage,
and the fin temperature cannot be raised because the TED voltage is at the maximum, the CCSM reduces the blower motor speed to achieve the
Temperature Set Point.
Cooled Seat Operation
When the cool seat switch is pressed for High Cool, the CCSM will transition to the COOL state. In response to this command, the CCSM applies a
