Air Mix Door Control (Automatic Temperature Control)

Introduction
The Electronic Automatic Temperature Control (EATC) system provides automatic regulation of the vehicle's interior temperature. The system is based on the operator selected "set temperature", regardless of the outside temperature changes. This is done by utilizing a microcomputer, also referred to as the EATC unit, which receives input signals from the following five sensors:
- Ambient temperature sensor
- In-vehicle temperature sensor
- Engine coolant ambient temperature sensor
- Sunload sensor
- PBR (Potentio Balance Resistor).

The EATC unit uses these input signals (including the set temperature) to automatically control:
- Outlet air volume
- Air temperature
- Air distribution.

Features

AIR MIX DOOR CONTROL (AUTOMATIC TEMPERATURE CONTROL)
The air mix door is automatically controlled so that in-vehicle temperature is maintained at a predetermined value by the temperature setting, ambient temperature, in-vehicle temperature and amount of sunload.

FRONT FAN SPEED CONTROL
The front blower speed is automatically controlled based on temperature setting, ambient temperature, in-vehicle temperature and amount of sunload.

When the EATC unit is set to AUTOMATIC, the blower motor starts to gradually increase air flow volume. When engine coolant temperature is low and vehicle interior warming is required under cold ambient conditions the blower motor operation is delayed to prevent cool air from flowing.

REAR FAN SPEED CONTROL
The rear blower speed can be controlled from the EATC unit or from the rear A/C control unit, when the rear fan switch (front) is set to REAR.

FRONT INTAKE DOOR CONTROL
When AUTOMATIC mode is selected, the front intake door is automatically controlled by: The temperature setting, ambient temperature, in-vehicle temperature and amount of sunload. The ON-OFF operation of the MAX A/C switch will allow manual control of the front intake door. The front intake door is set to the FRESH position when DEF or F/D mode is selected.

OUTLET DOOR CONTROL
The front mode outlet doors are automatically controlled by: The temperature setting, ambient temperature, in-vehicle temperature, and amount of sunload.

MAGNET CLUTCH CONTROL
The ECM controls compressor ON-OFF operation using signals from the throttle position sensor, low-pressure switch, high-pressure switch, engine coolant temperature sensor and EATC unit.

SELF-DIAGNOSTICS SYSTEM
The self-diagnostic system is built into the EATC unit to quickly locate the cause of problems.