Control Components

CONTROL COMPONENTS

Dual Automatic Temperature Control
The dual-zone electronic automatic temperature control (EATC) module analyzes input from the following major sources:
- Temperature, function and blower selection (made by the vehicle occupants)
- In-vehicle temperature
- Ambient temperature
- Sunload
- 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
- LH side temperature blend door position
- RH side temperature blend door position
- Panel airflow door position
- Floor airflow door position
- Defrost airflow door position
- Air inlet door position

Control System Inputs
The dual-zone EATC system has 6 control system inputs.

Dual-Zone EATC Module
The dual-zone EATC module:
- is located in the instrument panel.
- has a vacuum fluorescent display for displaying set temperature, function and diagnostic trouble codes (DTCs).
- utilizes an on-board diagnostic (OBD) feature to supply the technician with diagnostic trouble codes (DTCs). These DTCs direct the technician to the inoperative component.

Steering Wheel Audio/Climate Control Switch
The steering wheel audio/climate control switch:
- is located on the right side of the steering wheel.
- allows the driver to adjust the passenger compartment temperature setting and manually override the blower motor speed setting.

For removal and installation of the steering wheel audio/climate control switch, refer to Radio, Stereo, and Compact Disc.

Ambient Air Temperature Sensor
The ambient air temperature sensor and bracket:
- is located in front of the condenser core.
- contains a thermistor which measures the temperature of outside air as a resistance and sends that reading to the dual-zone EATC module.

In-Vehicle Temperature Sensor
The in-vehicle temperature sensor operates in the following manner:
- A thermistor in the in-vehicle temperature sensor measures air temperature inside the passenger compartment.
- An automatic temperature control aspirator hose and elbow is connected between the heater core and evaporator core housing and the in-vehicle temperature sensor.
- The automatic temperature control aspirator hose and elbow takes air from the heater core and evaporator core housing air stream to create a suction in the in-vehicle temperature sensor.
- The suction draws in-vehicle air into the in-vehicle temperature sensor and across the thermistor.

Solar Radiation Sensor
The solar radiation sensor supplies information to the dual-zone EATC module indicating LH side and RH side sunload. For information on the location and service of the solar amplifier, refer to Lighting and Horns.

PCM
The PCM supplies information about vehicle speed and engine coolant temperature to the dual-zone EATC for calculating ambient air temperature and blower speed respectively.

Control System Outputs
The dual-zone EATC system has 4 control system outputs.

Automatic Temperature Control (ATC) Solenoid and Manifold
The ATC solenoid and manifold:
- is located on the heater core and evaporator core housing near the blower motor.
- uses solenoid-type valves to distribute vacuum to the vacuum control motors based on the settings of the dual-zone EATC module.

Blower Motor Speed Control
The blower speed control:
- is located on the heater core and evaporator core housing near the blower motor.
- converts low power signals from the dual-zone EATC module to a high current, variable ground feed for the blower motor.
- varies the blower motor speed and is controlled by the dual-zone EATC module software.
- has a delay function to provide a gradual increase or decrease in blower motor speed under all conditions.
- controls the integral high blower speed relay which is engaged when maximum fan speed is selected.

Temperature Blend Door Actuators
The dual-zone EATC system utilizes 2 temperature blend door actuators to control 2 separate temperature blend doors that independently vary the LH side and RH side temperature settings, as desired. The temperature blend door actuators:
- are located on the heater core and evaporator core housing.
- move the temperature blend door on command from the dual-zone EATC module.
- contain a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the temperature blend door.
- are supplied a 5 volt signal and ground to the potentiometers. The voltage available at the wiper indicates the position of each potentiometer. The expressed value of the actuator wiper voltage is sent to the dual-zone EATC module and is matched with an expected wiper voltage value. The dual-zone EATC module then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the expected dual-zone EATC module wiper voltage value.

Vacuum Control Motors
The 4 vacuum control motors:
- are actuated by the ATC solenoid and manifold based on input from the dual-zone EATC module.
- position the airflow mode doors to direct system airflow to the vehicle interior as determined by the dual-zone EATC module settings.