Control System Inputs
The dual-zone EATC system has 4 control system inputs.
HVAC Module
The EATC system uses a remote HVAC module that is separate from the control interface. The Front Controls Interface Module (FCIM) provides the interface for the vehicle occupants to control the climate control system. When selections are made, the FCIM communicates the selections to the HVAC module through the Medium Speed Controller Area Network (MS-CAN), and the HVAC module adjusts the climate control system components to achieve the desired state. When the climate control system is operating in AUTO mode via command from the FCIM, the required climate control system settings are determined by the HVAC module. The HVAC module then adjusts the climate control system components to the desired state. The remote HVAC module is located under the driver side of the instrument panel.
In-Vehicle Temperature Sensor
The in-vehicle temperature sensor contains a thermistor which measures the in-vehicle air temperature and sends that reading to the HVAC module. An aspirator hose is connected between the heater core and evaporator core housing and the in-vehicle temperature sensor. The aspirator hose uses airflow through the heater core and evaporator core housing to create a venturi-type suction to draw in-vehicle air through the in-vehicle temperature sensor (across the thermistor).
Solar Radiation Sensor (Sunload Sensor)
The solar radiation sensor supplies information to the HVAC module indicating sunload.
Ambient Temperature Sensor
The ambient temperature sensor signal is received by the PCM and indicates the outside air temperature. The ambient temperature sensor is located in front of the radiator on the radiator support bolster.
Control System Outputs
The dual-zone EATC system has 4 control system outputs.
Blower Motor Speed Control
The blower motor speed control controls the blower motor speed by converting low power signals from the HVAC module to a high current, variable ground feed for the blower motor. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.
Temperature Blend Door Actuators
The dual-zone EATC system uses 2 temperature blend door actuators to control 2 separate temperature blend doors. The temperature blend doors independently vary the LH and RH side temperature settings, as desired. The temperature blend door actuators each contain a reversible electric motor and a potentiometer. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC module from the contact wiper indicates the position of the temperature blend door. The HVAC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected HVAC module contact wiper voltage value.
Airflow Mode Door Actuator
The airflow mode door actuator uses a cam and lever assembly to position the airflow mode doors on command from the HVAC module. The airflow mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC module to monitor the position of the airflow mode doors. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC module from the contact wiper indicates the position of the airflow mode doors.
Air Inlet Mode Door Actuator
The air inlet mode door actuator moves the air inlet door between the fresh and RECIRC positions on command from the HVAC module. The air inlet mode door actuator is driven to, and automatically stops at, the full RECIRC or full fresh air inlet position and does not require a potentiometer circuit to monitor its position.