Control System Inputs
The EMTC system has 2 system control inputs.
HVAC Module
The HVAC 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 HVAC 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 HVAC 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 HVAC 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 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.
Blower Motor Switch
The blower motor switch is mounted in the HVAC module and controls blower motor speed by adding or bypassing resistors in the blower motor resistor in all modes except OFF. The blower motor switch knob is removable and can be separately replaced.
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 climate control system in the AUTO mode. The HVAC module has a vacuum fluorescent display 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 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 HVAC 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 HVAC module for the outside air temperature display. Therefore, the ambient temperature PID monitored with a scan tool may not exactly match the HVAC module display. For information regarding the HVAC module outside air temperature display, refer to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION AND DIAGNOSTICS article.