System Description

Overview Of Control System:

Overview of Control System
The control system consists of
^ input sensors and switches,
^ the automatic amplifier (microcomputer), and
^ outputs.
The relationship of these components is shown in the above image.

Air Mix Door Control (Automatic Temperature Control)

Control System Output Components:

Component parts
Air mix door control system components are:
^ Auto amplifier
^ Air mix door motor (PBR)
^ In-vehicle sensor
^ Ambient sensor
^ Sunload sensor

System operation
Temperature set by Potentio Temperature Control (PTC) is compensated through setting temperature correction circuit to determine target temperature.
Auto amplifier will operate air mix door motor to set air conditioner system in HOT or COLD position, depending upon relationship between conditions.

Air Mix Door Control Specification:

Air mix door control specification

Air Mix Door Motor:

Air mix door motor
The air mix door motor is attached to the bottom of the heater unit. it rotates so that the air mix door is opened to a position set by the auto amplifier. Motor rotation is conveyed through a shaft and air mix door position. It is then fed back to the auto amplifier by PBR built-in air mix door motor.

Air Mix Door Operation:

Air mix door operation

PBR Characteristics:

PBR characteristics
Measure resistance between terminals (27) and (33) at vehicle harness side.

Mode Door Control

Mode Door Control:

Component parts
Mode door control system components are:
^ Auto amplifier
^ Mode door motor
^ PBR
^ In-vehicle sensor
^ Ambient sensor
^ Sunload sensor

System operation
The auto amplifier computes the air discharge conditions according to the ambient temperature and the in-vehicle temperature. The computed discharge conditions are then corrected for sunload to determine which outlets air will flow through into the passenger compartment.

Mode Door Control Specification:

Mode door control specification

Mode Door Motor:

Intake Door Control:

Mode door motor
The mode door motor is attached to the heater unit. It rotates so that air is discharged from the outlet set by the auto amplifier. Motor rotation is conveyed to a link which activates the mode door.

Intake Door Control

Mode Door Motor:

Components parts
Intake door control system components are:
^ Auto amplifier
^ Intake door motor
^ PBR
^ In-vehicle sensor
^ Ambient sensor
^ Sunload sensor

System operation
The intake door control determines intake door position based on the ambient temperature and the in-vehicle temperature. When the ECON, DEF, or OFF button is pushed, the auto amplifier sets the intake door at the FRESH position.

Intake Door Control Specification:

Intake door control specification

Intake Door Motor:

Intake door motor
The intake door motor is attached to the intake unit. It is set by the auto amplifier so that fresh air or interior air will be drawn into the passenger compartment. Motor rotation is conveyed to a lever which activates the intake door. Intake door motor operation.

Fan Speed Control
Component parts
Fan speed control system components are:
^ Auto amplifier
^ Fan control amplifier
^ PBR
^ In-vehicle sensor
^ Ambient sensor
^ Sunload sensor
^ Blower Hi-relay
^ Thermal transmitter

Fan Speed Control - System Operation:

System Operation

AUTOMATIC MODE
In the automatic mode, the blower motor speed is calculated by the automatic amplifier based on inputs from the:
^ PBR
^ in-vehicle sensor
^ sunload sensor
^ ambient sensor
The blower motor applied voltage ranges from approximately 4.5 Volts (lowest speed) to 12 Volts (highest speed).
To control blower speed (in the range of 4.5 V to 10.5 V), the automatic amplifier supplies a signal to the thermo control amplifier. Based on this signal, the thermo control amplifier controls the current flow from the blower motor to ground. If the computed blower voltage (from the automatic amplifier) is above 10.5 Volts, the high blower relay is activated. The high blower relay provides a direct path to ground (bypassing the blower amplifier), and the blower motor operates at high speed.

STARTING FAN SPEED CONTROL
Start up from COLD SOAK condition (Automatic mode)
In a cold start up condition where the engine coolant temperature is below 50° C (122° F), the blower will not operate for a short period of time (up to 180 seconds). The exact start delay time varies depending on the ambient and engine coolant temperature.
In the most extreme case (very low ambient) the blower starting delay will be 180 seconds. After this delay, the blower will operate at low speed until the engine coolant temperature rises above 50° C (122° F), at which time the blower speed will increase to the objective speed.

Start up from normal or HOT SOAK condition (Automatic mode)
The blower will begin operation momentarily after the AUTO button is pushed. The blower speed will gradually rise to the objective speed over a time period of 5 seconds or less (actual time depends on the objective blower speed).