Automatic Temperature Control (ATC) System

The Automatic Temperature Control (ATC) system provides automatic regulation of the vehicles interior temperature. The operator selects "set temperature", on which the regulation is based, regardless of the outside temperature changes. This is done by utilizing a microcomputer, also referred to as the automatic amplifier, which receives input signals from several sensors. The automatic amplifier uses these input signals (including the set temperature) to automatically control the ATC system's outlet air volume, air temperature, air distribution, bi-level door position and rear vent door position.

Air mix door control
The air mix door is automatically controlled so that in-vehicle temperature will reach, and be maintained at the operator selected "set temperature." For a given set temperature, the air mix door position will depend on: Ambient temperature, in-vehicle temperature, amount of sunload, and intake air temperature.

Fan speed control
Blower speed is automatically controlled based on temperature setting, ambient temperature, in-vehicle temperature, intake air temperature, amount of sunload and air mix door position.
With FAN switch set to "AUTO," the blower motor starts to gradually increase air flow volume.
When engine coolant temperature is low, the blower motor operation is delayed to prevent cool air from flowing.

Intake door control
The intake door position will be determined by: Ambient temperature, in-vehicle temperature, and whether the compressor is ON or OFF.

Outlet door control
The outlet door position will be determined by: Ambient temperature, in-vehicle temperature, intake air temperature, and amount of sunload.

Bi-level door control
Auto amplifier operates bi-level door based on mode door position, air mix door position and each sensor. Then it determines the discharge air temperature from VENT or DEF.

Rear vent door control
Rear vent door is controlled and operated by auto amplifier.

Compressor clutch control
The compressor operation (ON-OFF) is automatically controlled by the ambient sensor to prevent compressor damage in very cold ambient temperatures.

Self-diagnostic system
The self-diagnostic system consists of five steps. Each step can be accessed by pushing the switches on the automatic amplifier.
STEP 1: Checks LEDs and segments of the display.
STEP 2: Checks each sensor circuit for open or short circuit.
STEP 3: Checks mode door position and intake door position.
STEP 4: Checks operation of each actuator.
STEP 5: Checks temperature detected by each sensor, and detects multiplex communication error. AUXILIARY TRIMMER MECHANISM: Set temperature trimmer.

Memory function
With ignition switch turned OFF, the auto amplifier stores in memory the set temperature and inputs of various switches. When the ignition switch is turned ON, the system begins operation with the information stored in memory. The system, then immediately compensates for the actual operating conditions.