Heated Seats (Factory Installed)

Heated Seats Description and Operation (Factory Installed)

Heated Seat Components

The heated seat system consists of the following components:

* Heated seat switch

* HVAC control

* Seat memory control module or seat heating control module

* Seat cushion heating element

* Seat back heating element

* Seat cushion temperature sensor

* 25 A fuse

* 40 A fuse

Heated Seat Operation

The driver and passenger heated seats are controlled by separate heated seat switches. Both switches are located in the HVAC controls. When a heated seat switch is pressed, a LIN-Bus message is sent from the HVAC control to the HVAC control module. The HVAC control module then serves as a gateway to transmit the message to the seat memory control module/seat heating control module via serial data line indicating the heated seat command. In response to this message, the seat memory control module/seat heating control module applies or removes 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 HVAC control to either illuminate or turn off the appropriate temperature indicator.

Temperature Regulation

The seat memory control module/seat heating control 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 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.

Remote Start Seat Heating and Ventilation

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. When seat heating is commanded, the heating level will be on the "High" setting. On some vehicles, the LED display for the 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 turn 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.

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.