Control Components

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CONTROL COMPONENTS - HYBRID

Electronic Automatic Temperature Control (EATC)

The dual-zone EATC module analyzes input from the following major sources:

- Temperature, airflow mode, blower, A/C and RECIRC selection (made by the vehicle occupants)
- ECON button
- In-vehicle temperature sensor
- In-vehicle temperature and humidity sensor
- Ambient temperature sensor
- Sunload sensor (solar radiation sensor)
- Evaporator discharge air temperature sensor
- Vehicle speed
- Engine coolant temperature

Using these inputs, the dual-zone EATC module determines the correct conditions for the following outputs:

- A/C compressor ON/OFF request
- Blower motor speed
- Temperature blend door position
- Airflow mode door position
- Air inlet door position

Control System Inputs

The dual-zone EATC system has 4 control system inputs.

EATC Module (Climate Control Module)

The dual-zone EATC module provides an interface for the vehicle occupants to control the climate control system, or automatically controls the climate control system in the AUTO mode. The dual-zone EATC module uses the front display interface module for displaying set temperature, airflow direction, blower speed and DTCs. An on-board diagnostic (OBD) feature is incorporated to supply the technician with DTCs. These DTCs help direct the technician to the inoperative component.

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 dual-zone EATC 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).
The in-vehicle temperature sensor is mounted to the RH lower portion of the instrument cluster finish panel.

In-Vehicle Temperature and Humidity Sensor

The in-vehicle temperature and humidity sensor contains 2 thermistors, which separately measure the in-vehicle air temperature and humidity and send those readings to the EATC module. An aspirator hose and elbow is connected between the heater core and evaporator core housing and the in-vehicle temperature and humidity sensor. The aspirator hose uses airflow from the heater core and evaporator core housing air stream to create a Venturi-type suction to draw in vehicle air through the in-vehicle temperature sensor and across the thermistors.
The in-vehicle temperature and humidity sensor is mounted to the RH lower portion of the instrument cluster finish panel.

Sunload Sensor (Solar Radiation Sensor)

The solar radiation sensor supplies information to the dual-zone EATC module indicating sunload strength, and (to an extent) direction. The solar radiation sensor is located on the center of the instrument panel at the base of the windshield.

Ambient Temperature Sensor

The ambient temperature sensor signal is received by the dual-zone EATC module and indicates the outside air temperature. The ambient temperature sensor is located in front of the radiator on the bottom of the bumper beam.
The ambient temperature sensor signal is not the sole factor considered by the dual-zone EATC module for the outside air temperature display. Therefore, the ambient temperature PID monitored with a scan tool may not exactly match the dual-zone EATC module display.

Control System Outputs

The EATC system has 4 control system outputs. When operating in AUTO mode, the control system outputs will be automatically adjusted by the dual-zone EATC module.

NOTE: Each of the 4 control system outputs may be overridden by the passenger if desired.

Blower Motor Speed

The blower motor speed control controls the blower motor speed by converting low power signals from the dual-zone EATC module to a high-current, variable ground feed for the blower motor. A delay function is used to provide a gradual increase or decrease in blower motor speed under all conditions.

Temperature Blend Door Position

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 side 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 return circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal returned to the dual-zone EATC module from the contact wiper indicates the position of the temperature blend door. The dual-zone EATC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected dual-zone EATC module contact wiper voltage value, as determined by the control algorithm.

Airflow Mode Door Position

The airflow mode door actuator uses a cam and lever assembly to position the airflow mode doors on command from the dual-zone EATC module. The mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the dual-zone EATC 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 return circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal returned to the dual-zone EATC module from the contact wiper indicates the position of the airflow mode doors. The dual-zone EATC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected dual-zone EATC module contact wiper voltage value, as determined by the control algorithm.

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 dual-zone EATC module. The air inlet mode door actuator is driven to, and will automatically stop at, the full RECIRC or full fresh air inlet position and does not require a potentiometer circuit to monitor its position. The airflow mode door does not stop at any point between the RECIRC or fresh air inlet position.