Heated/Vented Seat

Heated/Vented Seat Description and Operation

Heated Seat Components

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

* Radio/HVAC controls with heated and vented seat switches

* Body control module

* Seat heating control module

* Seat cushion heating element

* Seat back heating element

* Seat temperature control module

* Seat cushion blower motors

* Seat back blower motors

Heated/Vented Seat Switches

The driver and passenger heated seats switches are located in the radio/HVAC faceplate controls. The body control module (BCM) monitors each switch activation to determine whether heat or ventilation mode has been requested and to what level. With each press of the switch, the system will cycle through High, Medium, Low, and then back to Off again.

When a heated or vented seat switch is pressed, a LIN bus serial data message is sent from the radio/HVAC controls to the HVAC control module. In turn the HVAC control module sends a low speed GMLAN serial data message to the body control module (BCM) indicating the heated/vented seat command. The BCM serves as the heated/vented seat system master to determine the requested operating mode. The BCM then sends a LIN bus serial data message to the seat heating control module indicating the heated/vented seat command. The BCM also controls the seat temperature and mode indicators, via the serial data line, used to provide the operator with feedback as to the operating status of the system.

Heated Seat Operation

When the seat heating control module receives a heated seat command, it applies a high side drive pulse width modulated (PWM) signals driven at the required duty cycles to generate the appropriate effective voltage to the heating elements to attain the commanded seat temperature.

This heated seat system utilizes a self-regulating heating element system, which is different from the non-regulated heating element systems with seat temperature sensors previously used on GM vehicles. In the self-regulating type of system, temperature feedback to a control module is not required for temperature regulation. The heating element material itself regulates the surface temperature based on the effective voltage applied to the heating element.

Vented Seat Operation

Each vented seat consists of 4 blower motors and a seat temperature control module. There are 2 blower motors packaged with the seat back heating element and 2 blower motors along with the temperature control module packaged with the seat cushion heating element. The vented seat operation is designed to draw cabin air around and away from the occupant through small holes in the seat covers, through channels in the foam pad, and then through the blower motor exhausting the waste air under the seat cushion.

With the ignition ON, battery voltage is applied from the ignition run relay and through a 7.5 A fuse to the seat temperature control module. Ground for the blower motors is provided from the ground circuit and the ground connection.

When the seat heating control module receives a ventilation seat command, it sends a low side drive pulse width modulation (PWM) signal through the blower motor control circuit to the seat temperature control module indicating the seat ventilation command. The module interprets this signal then applies ignition voltage to the blower motors and sends a high side drive PWM signal to the seat back and cushion blower motors indicating the vented seat command. The logic in the blower motors then sets the blower speed to the switch set point. All blower motors run drawing cabin air around and away from the occupant.

Load Shed 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 Description and Operation.