Heated/Vented Seat Description and Operation
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Heated/Vented Seat Description and Operation
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The heated/vented seat system consists of the following components:
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Seat memory control module or seat heating control module
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Seat cushion heating element
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Seat back heating element
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Seat cushion temperature sensor
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Seat cushion blower motor
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The driver and passenger heated seats are controlled by separate heated seat switches that are located with the radio/HVAC controls. When a heated seat switch is pressed, a serial data message is sent from the radio/HVAC controls to the HVAC control module indicating the heated seat command. The HVAC control module serves as a gateway to transmit the message to the seat memory control module/seat heating control module via the serial data line. In response to this message, the seat memory control module/seat heating control module applies battery voltage through the element supply voltage circuit of the seat heating elements. The seat memory control module/seat heating control module sends a serial data message back to the HVAC control module to gateway the information to the radio/HVAC controls to either illuminate or turn off the appropriate temperature indicator.
The heated/vented seat system is designed to warm or cool the seat cushion and seat back to 3 different temperature settings: High, Medium and Low. The seat memory control module/seat heating control module supplies the seat temperature sensor with a 5 V reference signal circuit and a the low reference circuit. The temperature sensor (thermistor) is located just under the seat cushion cover with the heater element. The sensor is a variable resistor; its resistance changes as the seat temperature changes causing the voltage on the signal circuit to change. The module monitors this voltage to determine the temperature of the seat. Once the seat reaches the set temperature, the module will then cycle the low side control circuit of the heating elements ON and OFF in order to maintain the desired temperature.
The vented seat operation is designed to draw cabin air around and away from the occupant through small holes in the seat cushion and seat back covers, through channels in the foam pad, and then through the blower motor exhausting the waste air under the seat cushion.
The driver and passenger vented seats are controlled by separate vented seat switches located in the with the radio/HVAC controls. With the ignition ON, ignition voltage is supplied to the driver and passenger seat blower motors through a 15 A fuse that is located in the rear body fuse block. Ground from G301 is provided to the driver seat blower motors while ground from G300 is provided to the passenger seat blower motors. When a vented seat switch is pressed, a serial data message is sent from the radio/HVAC controls to the HVAC control module indicating the vented seat command. The HVAC control module serves as a gateway to transmit the message to the seat memory control module/seat heating control module via the serial data line. In response to this message, the seat memory control module/seat heating control module applies a low side pulse width modulation (PWM) signal through the blower motor control circuits to the seat cushion and seat back blower motors indicating the vented seat command. The logic in the blower motors then sets the blower speed to the switch set point. Both blower motors run drawing cabin air around and away from occupant. The seat memory control module/seat heating control module then sends a serial data message back to the HVAC control module to gateway the information back to the radio/HVAC controls to either illuminate the appropriate switch indicator.
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Remote Start Seat Heating and Ventilation
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Some vehicles allow the customer to configure their heated and/or ventilated seats to come on after a remote start is commanded. The heated seats will only come on if the outside air temperature is below 50°F as measured by the outside air temperature sensor. Seat ventilation will only come on if the outside air temperature is measured above 80 °F. When seat heating is commanded, the heating level will be on the "High" setting. On some vehicles, the LED display for the heating or ventilation temperature level may not illuminate during remote start operation. When the vehicle operator inserts the key in the ignition and turns it to the "On" position, the heated seats will automatically be switched off. Be aware that during remote start heated seat operation, since there is no occupant in the seat, the customer may comment that they feel little or no difference in the temperature of the seat. This is due to little heat transfer to the seat cover occurring since there is no weigh on the cushion. Once the seat is occupied and the seat cover is pressed against the heater element, heat will begin to transfer more rapidly to the seat cover.
The electrical power management function is designed to monitor the vehicle electrical load and determine when the battery is potentially in a high discharge condition. The heated/cooled seat system is one of the vehicle loads that is subject to reduction during a battery discharge condition. For more information on load management refer to
Electrical Power Management Description and Operation
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