For 1990-2009 cars

### Heated Seat Components

The heated/vented seat system consists of the following components:

• | Heated seat switch

• | Vented seat switch

• | HVAC control panel

• | Memory seat module or Heated seat module

• | Seat cushion heating element

• | Seat back heating element

• | Seat cushion temperature sensor

• | Seat cushion blower motor

• | Seat back blower motor

• | F53UA Fuse 10 A

• | F33UA 25 A

### Heated Seat Operation

The driver and passenger heated seats are controlled by separate heated seat switches. Both switches are located in the integrated center stack (ICS). When a heated seat switch is pressed, a serial data message is sent to the HVAC module. The HVAC module then serves as a gateway to transmit the message to the memory seat module/heated seat module via serial data line indicating the heated seat command. In response to this signal, the memory seat module/heated seat module applies or removes battery voltage through the element supply voltage circuit of the seat heating elements. The memory seat module/heated seat module sends a serial data message back to the HVAC module to gateway the information to the ICS to either illuminate or turn off the appropriate temperature indicator.

### Temperature Regulation

The memory seat module/heated seat module monitors the seat temperature through the temperature sensor signal circuit and the temperature sensor (thermistor) located in the seat cushion with the heater element. The temperature sensor is a variable resistor, it's resistance varies as the temperature of the seat changes. When the temperature sensor resistance indicates to the memory seat module/heated seat module that the seat has reached the desired temperature, the module opens the ground path of the seat heating elements through the heated seat element control circuit. The module will then cycle the element control circuit open and closed in order to maintain the desired temperature.

### Vented Seat Operation

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 integrated center stack (ICS) with the HVAC controls. With the ignition ON, Ignition voltage is supplied to the driver and passenger seat blower motors through the F53UA fuse located in the underdood fuse block. Ground from G305 is provided to the driver and passenger seat blower motors. When a vented seat switch is pressed, a serial data message is sent to the HVAC module. The HVAC module serves as a gateway to transmit the message to the memory seat module/heated seat module via the serial data line indicating the vented seat command. In response to this message, the memory seat module/heated seat 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 memory seat module/heated seat module then sends a serial data message back to the HVAC module to gateway the information back to the ICS to either illuminate or turn off the appropriate switch indicator.

### Load Management

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 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.