Control Components

CONTROL COMPONENTS

ELECTRONIC MANUAL TEMPERATURE CONTROL
The electronic manual temperature control (EMTC) components are used to select the following:
- Air inlet source (outside or recirculated)
- Blower motor speed
- Discharge air temperature (temperature blend)
- Discharge air location (defrost, panel, floor)
- A/C compressor operation

Control System Inputs
The EMTC system has 2 system control inputs.

EMTC Module (Climate Control Module)
The EMTC module integrates the temperature control, airflow mode selection, A/C request button, recirculated air request button and rear defog switch into a single unit.

The temperature control selector setting determines air temperature. Movement of the temperature display from COOL (blue) to WARM (red) causes a corresponding movement of the temperature blend door and determines the discharge air temperature that the air distribution system will maintain. The temperature control selector is an integral part of the EMTC module and cannot be installed separately. The temperature selector knob is removable and can be separately replaced.

The airflow mode setting determines air discharge location. Movement of the airflow mode selector causes a corresponding movement of the airflow mode doors and determines the air discharge location. The airflow mode selector is an integral part of the EMTC module and cannot be installed separately. The airflow mode selector knob is removable and can be separately replaced.

The A/C request button determines A/C compressor operation, except when the airflow mode selector is in the OFF, MAX A/C or DEFROST mode. The A/C request button is an integral part of the EMTC module and cannot be installed separately.

The recirculated air request button can select recirculated air in any mode except DEFROST, and fresh air in any mode except MAX A/C or OFF. The recirculated air request button is an integral part of the EMTC module and cannot be installed separately.

The rear defog button signals activation of the heated backlight. The rear defog button is an integral part of the EMTC module and cannot be installed separately.

Control System Outputs
The EMTC system has 4 system outputs.

Temperature Blend Door Actuator
The temperature blend door actuator moves the temperature blend door on command from the EMTC module.

The temperature blend door actuator contains 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 EMTC module from the contact wiper indicates the position of the temperature blend door. The EMTC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected EMTC 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 EMTC module. The mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the EMTC 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 EMTC 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 EMTC 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.

ELECTRONIC AUTOMATIC TEMPERATURE CONTROL
The dual-zone electronic automatic temperature control (EATC) module analyzes input from the following major sources:
- Temperature, airflow mode, blower, A/C and RECIRC selection (made by the vehicle occupants)
- In-vehicle temperature sensor
- Ambient temperature sensor
- Solar radiation sensor
- Evaporator 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 operation
- Blower 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 has a vacuum fluorescent display for displaying set temperature, airflow direction, blower speed and diagnostic trouble codes (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).

Solar Radiation Sensor (Sunload Sensor)
The solar radiation sensor supplies information to the dual-zone EATC module indicating sunload.

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 radiator support bolster.

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.

Blower Motor Speed Control
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 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 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 EATC module from the contact wiper indicates the position of the temperature blend door. The EATC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected EATC 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 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.

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.