Heated Seat Components
The rear heated seat system has one control module that controls heat operation for both the left and right rear seat. The rear heated seats consist of the following components:
| • | Rear heated seat control module |
| • | Left rear heated seat switch |
| • | Right rear heated seat switch |
| • | Left seat cushion heating element |
| • | Left seat back heating element |
| • | Left seat cushion temperature sensor |
| • | Right seat cushion heating element |
| • | Right seat back heating element |
| • | Right seat cushion temperature sensor |
| • | RR HTD/SEAT (DTS) fuse 20 A |
Power and Grounds
Battery positive voltage is supplied to the rear heated seat module from the RR HTD/SEAT (DTS) fuse that is located in the rear fuse block. This voltage is used to power up the heated seat module and to supply power to the seat heater elements. The rear
heated seat module is grounded through the module ground circuit and G301.
Modes of Operation
There are 2 modes of operation available for heated seats; both the seat cushion and seat back heat, or seat back only heat. When a heated seat temperature signal request is received, the heated seat module will activate both the seat cushion and seat
back heating elements. When the heated seat BACK ONLY mode button is pressed once the heated seat module will deactivate the seat cushion heating element and leave the seat back heating element ON.
Heated Seat Switch/LED Indicators and System Operation
The left and right rear heated seats are controlled by separate heated seat switches located in the rear door panels. Ground is supplied to the rear heated seat switches through the switch ground circuits from their respective ground stakes. G301 for the
left rear switch and G304 for the right rear switch. Battery voltage is supplied to the heated seat switch indicators through the LED dimming supply circuit from the body control module (BCM). The rear heated seat module controls the heated seat operation for
both, the left and right rear heated seats, and the heated seat switch temperature indicators.
The following describes the sequence of operation and how the heated seat module responds to each of the switch inputs.
| • | High Temperature--When the heated seat switch is pressed once, ground is applied through the switch contacts and the switch signal circuit to the rear heated seat module indicating the high heat request. In response to this signal, the module
applies battery positive through the heating element supply voltage circuits to the seat cushion and seat back heating elements. At the same time, it supplies a ground through the heating low reference circuits to the seat heating elements. The module then applies
a ground through the 3 temperature indicator control circuits illuminating all 3 LEDs indicating the high temperature mode. |
| • | Medium Temperature--When the switch is pressed a second time, the heated seat module sets the temperature level to medium heat. Then it removes the ground from the high temperature indicator leaving 2 LEDs illuminated indicating the medium
temperature mode. |
| • | Low Temperature--When the switch is pressed a third time, the heated seat module sets the temperature level to low heat. Then it removes the ground from the medium temperature indicator leaving 1 LED illuminated indicating the low temperature
mode. |
| • | System OFF State--When the switch is pressed a fourth time, the heated seat module removes the battery voltage and grounds from the heating elements. Then it removes the ground from the low temperature indicator, indicating the system OFF state. |
| • | Back Only Mode-When the heated seat is ON and the BACK ONLY mode button is press, ground is applied through the switch contacts and the heated seat back only mode signal circuit to the rear heated seat module. In response to this signal, the
module turns OFF power to the seat cushion, leaving the seat back active. The module then applies a ground through the heated seat back only mode indicator control circuit illuminating the back only mode indicator. |
Temperature Regulation
The heated seat system is designed to warm the seat cushion and seat back to approximately 42°C (107.6°F) when in the high position, 39.5°C (103°F) when in the MED position, and 37°C (98.6°F) when in the low position. The heated
seat module monitors the seat temperature through the temperature sensor signal circuits and the temperature sensors (thermistor) that are located in the seat cushion and the seat back. The temperature sensors are variable resistors, their resistance varies
as the temperature of the seat changes. When the temperature sensor resistance indicates to the heated seat module that the seat has reached the desired temperature, the module opens the high side driver supply voltage to the seat heating elements. It will then
cycle the high side driver supplying power to the elements open and closed in order to maintain the desired temperature.
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/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
.
