Control Components

Control Components

Electronic Manual Temperature Control (EMTC)

The Electronic Manual Temperature Control (EMTC) components are used to control:

- air inlet source (outside or recirculated).
- blower motor speed.
- discharge air temperature (temperature blend).
- discharge air location (defrost, panel, floor).
- A/C compressor operation.

Remote Start Operation

The climate control system conditions the cabin interior when remote start has been activated. The operating mode and temperature are automatically selected by the HVAC module based on the outside ambient temperature. When the ignition switch is cycled to the ON position, the HVAC module settings will revert to the settings present when the ignition switch was last switched OFF.

Electronic Manual Temperature Control (EMTC) System Inputs

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 the air distribution system will maintain. The temperature control selector is an integral part of the HVAC module and cannot be installed separately.

The airflow mode setting determines air discharge location. Pressing each airflow mode selector button causes a corresponding movement of the airflow mode doors and determines the air discharge location. The airflow mode selector buttons are an integral part of the HVAC module and cannot be installed separately.

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 HVAC module and cannot be installed separately.

The recirculated air request button selects 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 HVAC 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 HVAC module and cannot be installed separately.

The blower motor speed setting controls blower motor speed in all modes except OFF. The blower motor speed selector is an integral part of the HVAC module and cannot be installed separately.

Electronic Manual Temperature Control (EMTC) System Outputs

The EMTC system has 4 control system outputs.

Blower Motor Speed

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. The HVAC module adjusts blower motor speed based on the blower motor speed selector position. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

The blower motor speed control is located on the heater core and evaporator core housing behind the glove compartment.

Temperature Blend Door Position

The temperature blend door actuator moves the temperature blend door on command from the HVAC 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 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 powers the actuator motor to move the temperature blend door to the desired position. The desired position is set by the vehicle occupants using the temperature selector.

The temperature blend door actuator is located on the top of the heater core and evaporator core housing.

Airflow Mode Door Position

The defrost/panel/floor airflow mode door actuator uses a cam, lever and cable assembly to position the airflow mode doors on command from the HVAC module. The defrost/panel/floor 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. The HVAC module powers the actuator motor to move the airflow mode doors to the desired position. The desired position is set by the vehicle occupants using the mode selector buttons.

The defrost/panel/floor airflow mode door actuator is located on the heater core and evaporator core housing to the right of the steering column, and is part of an assembly with the defrost/panel/floor mode door actuator actuating assembly.

Air Inlet Mode Door Position

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. The air inlet mode door does not stop at any point between the RECIRC or fresh air inlet position.

The air inlet mode door actuator is located on the air inlet duct behind the glove compartment.

Dual-Zone Electronic Automatic Temperature Control (EATC)

The HVAC module analyzes input from the following major sources:

- Temperature, airflow direction, blower, A/C and RECIRC selection (made by the vehicle occupants)
- In-vehicle temperature sensor
- Ambient temperature sensor
- Sunload sensor (solar radiation sensor)
- Vehicle speed
- Engine coolant temperature

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

- A/C compressor operation
- Blower speed
- RH and LH temperature blend door positions
- Defrost/panel/floor airflow mode door position
- Air inlet mode door position

Remote Start Operation

The climate control system conditions the cabin interior when remote start has been activated. The operating mode and temperature automatically selected by the HVAC module are based on the outside ambient temperature. When the ignition is cycled to the ON position, the HVAC module settings will revert to the settings present when the ignition switch was last switched OFF.

Electronic Automatic Temperature Control (EATC) System Inputs

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

HVAC Module

The HVAC module provides an interface for the vehicle occupants to control the climate control system, or automatically controls the system in the AUTO mode.

The HVAC module is mounted to the center instrument panel finish panel below the Audio Control Module (ACM).

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).

The in-vehicle temperature sensor is mounted to the instrument panel to the right of the steering column.

Sunload Sensor (Solar Radiation Sensor)

The sunload sensor supplies information to the dual-zone HVAC module indicating sunload. When sunload is detected, the information from the sensor is used to lower the A/C temperature output to compensate for radiant heat warming the vehicle interior and occupants.

The sunload 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 HVAC module and indicates the outside air temperature. The ambient temperature sensor is located in the bottom of the RH exterior mirror housing.

The ambient temperature sensor signal is not the only factor the HVAC module considers for the outside air temperature display. Therefore, the ambient temperature PID monitored with a scan tool may not exactly match the display. Refer to Climate Control System - General Information and Diagnostics Testing and Inspection.

Electronic Automatic Temperature Control (EATC) System Outputs

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

The EATC system has 4 control system outputs. When operating in AUTO mode, the control system outputs are automatically adjusted by the HVAC module.

Blower Motor Speed

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. The HVAC module adjusts blower motor speed based on the difference between the in-vehicle temperature sensor signal and set temperature. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

The blower motor speed control is located on the heater core and evaporator core housing near the blower motor.

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 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 powers the actuator motors to move the temperature blend doors to the desired positions. The desired temperature blend door positions are calculated by the HVAC module based on the set temperature, in-vehicle temperature, ambient temperature and sunload.

The LH temperature blend door actuator is located on the bottom of the heater core and evaporator core housing. The RH temperature blend door actuator is located on the top of the heater core and evaporator core housing.

Airflow Mode Door Position

The defrost/panel/floor airflow mode door actuator uses a cam, lever and cable assembly to position the airflow mode doors on command from the HVAC module. The defrost/panel/floor 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. The HVAC module powers the actuator motor to move the airflow mode doors to the desired position. The HVAC module determines the desired airflow mode door position based on the calculated outlet temperature.

The defrost/panel/floor airflow mode door actuator is located on the heater core and evaporator core housing to the right of the steering column.

Air Inlet Mode Door Position

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. The air inlet mode door does not stop at any point between the RECIRC or fresh air inlet position.

The air inlet mode door actuator is located on the air inlet duct behind the glove compartment.