For 1990-2009 cars

### Heated Seat Components

The cooled seat system consist of the following components:

• | Cooled seat switch

• | Memory seat module

• | Seat cushion ventilation cooling module

• | Seat back ventilation cooling module

• | Seat cushion temperature sensor

• | Seat back temperature sensor

• | HTD/SEAT Fuse 30 A

### Air Circulation

When the cool seat switch is pressed to initiate operation of the cooled seat system, cabin air is drawn through the ventilation cooling module air filter, then directed through passages in the foam of the seat cushion and seat back to the seat's occupant. In order for the cooled seat system to operate to its optimum performance, it is crucial to have unrestricted air flow through the system. A dirty or restricted air filter, the blockage of an exhaust air duct, a misaligned cool ventilation module, or incorrect foam installation of the seat cushion or seat back will all have negative effects on the cooled seat operation.

### Ventilation Cooling Module Power and Grounds

Battery positive voltage is supplied at all times to the driver and passenger seat ventilation cooling modules through the HTD/SEAT fuse located in the I/P fuse block. Ground for the driver seat ventilation modules is provided at G303, while ground for the passenger seat ventilation modules is provided at G302.

### Ventilation Cooling Module

Each cooled seat has 2 ventilation modules, one located under the seat cushion and one located in the seat back. These modules are controlled by a PWM signal from the memory seat module (MSM) and the cooled seat switch located in the center console. Each ventilation module contains a thermo-electric device (TED) and a blower motor. The TED is mounted downstream of the blower motor. Each TED consists of a circuit of positive and negative connections sandwiched between 2 ceramic plates. Each ceramic plate is equipped with copper fins for cool/heat exchange. The air flowing past these fins is either directed as cooled air into the seat cushion and seat back, or directed into the cabin as worm waste air.

### Cooled Seat Switches and Door Modules

The driver and front passenger seats are controlled by separate cool seat switches. Ground is supplied to the cool seat switch through the low reference circuit from the respective door module. The door module plays an important part of the cooled seat operation; first by relaying the selected switch inputs to the MSM, and second, by controlling the temperature indicators of the switch.

The following describes the sequence of operation of the cool seat switch, and how the door module responds to each of the switch inputs.

• | High Cool Mode - When the cool seat switch is pressed once, ground is applied through the switch contacts and the switch signal circuit to the door module. In response to this signal, the door module sends a serial data message to the memory seat module (MSM). In response to this message, the MSM then sends a pulse width modulation (PWM) signal through the cool seat mode signal circuit to the ventilation cooling modules indicating the high cool command. The door module then applies a ground through the high, medium, and low indicator control circuits of the switch illuminating all 3 indicators, indicating the high cool mode.

• | Medium Cool Mode - When the switch is pressed a second time, the door module signals the MSM, the MSM then relays the message to the ventilation modules of the medium cool mode request. The door module then removes the ground from the high mode indicator, leaving the medium and low indicators illuminated, indicating the medium cool mode.

• | Low Cool Mode - When the switch is pressed a third time, the door module signals the MSM, the MSM then relays the message to the ventilation modules of the low cool mode request. The door module then removes the ground from the medium mode indicator, leaving the low mode indicator illuminated, indicating the low cool mode.

• | System Off State - After the switch is pressed a fourth time, the door module signals the MSM, the MSM then relays the message to the ventilation modules of the system OFF request. The door module then removes the ground from the low indicator control circuit turning OFF the low mode indicator.

### Temperature Regulation

The ventilation cooling modules supply a 5 V reference voltage through the temperature sensor signal circuit and ground through the temperature sensor low reference circuit to the respective seat cushion and seat back temperature sensors. The sensors are variable resistors, their resistance varies as the temperature of the seat changes. When the temperature sensor resistance indicates to the ventilation module that the seat has reached the desired temperature, they will set the blower speed 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 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.