System Description

The Electronic Automatic Temperature Control (EATC) system controls all functions for the heating, ventilation and air conditioning systems to achieve interior comfort. The EATC automatic function maximizes interior comfort without driver intervention. Manual adjustments can be made to the automatic control for both mode function and blower speed function.

The EATC climate control assembly uses a microcomputer to analyze input from these sources:
^ A/C ambient air temperature sensor (outside).
^ Cold Engine Lockout (CELO) switch.
^ Automatic temperature control sensor (interior).
^ A/C compressor.
^ Sunload sensor.

Additional inputs to the system are function, temperature, and blower speed, which may be adjusted by the driver using the buttons on the EATC climate control assembly.

The EATC climate control assembly uses these inputs to determine:
^ A/C clutch engagement.
^ Blower motor speed strategy.
^ Front and auxiliary blend door position.
^ Air intake door position.
^ Mode door (panel, defrost, floor) selection.

A self-diagnostic mode is included in the EATC climate control assembly. The EATC climate control assembly detects and stores Diagnostic Trouble Codes (DTCs) for malfunctions in the EATC system. The DTCs pinpoint both hard and intermittent faults that occur in the EATC system.






CONTROL ASSEMBLY
The Electronic Automatic Temperature Control (EATC) climate control assembly has three main features:
^ Temperature control.
^ Air flow control.
^ Blower motor control.

Temperature Control
With the system operating under automatic control, the Vacuum Fluorescent Display (VFD) will show AUTO and the preferred or target temperature which the EATC system maintains. Temperature selection may be increased or decreased by pressing the TEMP button. The temperature can be adjusted between a maximum cool setting of 15°C (60°F) to a maximum heat setting of 32°C (90°F).

Air Flow Control
The EATC climate control assembly includes air flow control positions for OFF, mix, defrost, panel, panel/floor, floor and AUTOMATIC. With the system operating under automatic control, air is directed to the appropriate ducts, depending on the sensor inputs, temperature selection and current state. The EATC system has the option to manually override the automatic control functions to change mode without leaving the automatic temperature or fan speed selection.

Blower Control
Under automatic control, blower motor speed varies as required to accommodate the automatic functions in the system. The blower motor control for the blower speed determines the speeds at which the blower motor operates. Each position of the blower motor control wheel is detented for positive engagement. Under manual control, blower speed is constant based on the blower motor control setting.

The EATC controls the rear fan and the rear blend door. Rear blower speed is selected through the EATC rear control switch in position 1, 2, 3, or 4 or the rear control switch in the rear position.