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Home >> Cadillac >> 2006 >> DTS V8-4.6L VIN Y >> Repair and Diagnosis >> Body and Frame >> Seats >> Seat Temperature Element >> Description and Operation >> Heated Seats - Rear

Heated Seats - Rear



HEATED SEATS DESCRIPTION AND OPERATION - REAR

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
- FRT/RR HTD/SEATS Fuse 20 A

POWER AND GROUNDS
Battery positive voltage is supplied to the rear heated seat module from the FRT/RR HTD/SEATS 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 G?.

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. Press the heated seat BACK ONLY button a second time and the heated seat module will reactivate the seat cushion heating element.

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 panel. Ground is supplied to the heated seat switch from the switch ground circuit and G? 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 activates the low side drivers that supply a ground through the heating element control circuits to the seat heating elements. The module then applies a ground through the high temperature indicator control circuit illuminating the high temperature indicator to indicate 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 and applies ground to the medium temperature indicator to indicate 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 and applies ground to the low temperature indicator to indicate 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 the seat cushion heat, by opening the ground path for the seat cushion heating element control circuit. The module then applies a ground through the heated seat back only mode indicator control circuit illuminating the back only indicator to indicate the back only mode.

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 ground path of the seat heating elements through the heated seat element control circuit. The module will then cycle the low side driver element control circuits 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.
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