Opel Frontera UE. Manual - part 635

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

1A–97

Overview of Construction, Movement
and Control of Major Parts of
Automatic Air Conditioner System

Automatic Heater/Air Conditioner Control
Unit

Equipped with the built-in micro-computer, this control
unit operates on signals from sensors and input signals
from switches to offer total control of the blower fan, and
actuators used for the mode door, intake door and air
mix door.
Its self-diagnosis function enables quicker access to a
failed part and its more accurate troubleshooting.

In Car Sensor

It is a sensor used for detecting room temperature of a
vehicle. This sensor converts a given room temperature
into a resistance value before entering the data to the
automatic heater/air conditioner control unit.
This in car sensor unites the power driven aspirator and
the motor fan so that a small amount of room air may be
constantly fed to the sensor.
This sensor is provided on the control panel.

865RX015

EndOFCallout

Ambient Sensor

This sensor is used for detecting temperature outside
the vehicle. It converts a given outside air temperature
into a resistance value before entering the data to the
automatic heater/air conditioner control unit.
Thermal effects from the condenser and radiator during
idling after a run can be measured and offset the
automatic amplifier.
This sensor is provided on the side plate situated at
upper right side of the condenser.

875RY00021

EndOFCallout

Duct Sensor

The duct sensor is the sensor to detect temperature
change of the side of evaporator blower coming by fresh
recirculation of intake door or “on" “off" of compressor.
The temperature is converted to resistant rate.
And it works as thermostat to control to prevent freezing
of evaporator.
This sensor is installed in the upper case of evaporator.

874RX014

EndOFCallout

Legend

(1) In Car Sensor
(2) Automatic Air Conditioner Control Unit

Legend

(1) Ambient Sensor

Legend

(1) Evaporator Core
(2) Duct Sensor
(3) Lower Case
(4) Upper Case

1A–98

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Sun Sensor

It is a photodiode used for detecting quantity of solar
radiation. This sensor converts the offset signal
generated by changes in the interior temperature (which
results from fluctuations in solar radiation) into
photoelectric current to enter into the automatic heater/
air conditioner control unit.
This sensor is provided at top of the defroster grill.

865RW009

EndOFCallout

Power Transistor

Receiving base current from the automatic heater/air
conditioner control unit, the power transistor implements
stage-less speed change of the blower fan motor. This
transistor is provided on the evaporator.

874RX015

EndOFCallout

Max Hi Relay

This relay turned on or off by the signal from the
automatic heater/air conditioner control unit. As the
Max Hi relay is turned on, supply voltage is directly fed
to the blower fan motor to select the Max Hi mode.

860RW028

EndOFCallout

Actuator

The actuators are power driven type containing a small
motor. Receiving output current from the automatic
heater/air conditioner control unit, actuators drive the
heater and blower unit mode doors.
Actuators consist of the mode actuator used for
switching the mode (blow port selection), the mix
actuator used for changing aperture of the air mix door,
the intake actuator used for switching the intake
mode(fresh air/interior air) and the cold air bypassing
actuator.

860RW029

Legend

(1) Sun Sensor

Legend

(1) Evaporator Assembly
(2) Power Transistor

Legend

(1) Blower Unit
(2) Max High Relay

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

1A–99

EndOFCallout

The actuator changes the motor speed using the gear
and drives each door rotating the output axis united with
the sliding contact.

860RW026

EndOFCallout

The mode and mix actuators are common actuators
with the built-in potentiometer. For the intake actuator,
the contact switch type is selected.
The potentiometer is a register assembled to the printed
circuit board of the mix and mode actuators. It detects
the air mix door position specified by rotation of the
output axis as a ratio of the variable terminal (VM)
voltage against the reference voltage (VDD: 5V), then
signals the value to the automatic heater/air conditioner
control unit.

C01RX016

Movement of Mix Actuator

Position of the air mix door is determined by the
controller on the automatic heater/air conditioner control
unit.
As the heat or cool side of the controller is grounded,
the transistor on the driver is activated and, thus, the
motor rotation is turned on. The sliding contact
connected to the motor sends the position detection
signal from the potentiometer to the automatic heater/air
conditioner control unit. As the set temperature and
interior temperature are balanced, the controller returns
to the neutral and the motor rotation is stopped.

C01RX005

Legend

(1) Mix Actuator
(2) Heater Unit
(3) Intake Actuator
(4) Mode Actuator
(5) Blower Unit

Legend

(1) Output Axis
(2) Motor
(3) Printed Circuit Board
(4) Sliding Contact

C-45

Rotation

direction

Remarks

(+) side

(-) side

Clockwise

Full heat side

Counter

clockwise

Full cool side

1A–100

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Movement of Mode Actuator

As target position of the mode door is decided on the
controller of the control unit, the control unit reads the
position detection signal from the actuator to select the
clockwise or counter clockwise motor rotation direction.
Grounding the controller VENT or DEF side after the
direction selection activates the transistor on the driver,
thus turning on the motor rotation. Accompanying the
motor rotation, the sliding contact rotates, too. When
the target position is reached, the controller on the
control unit returns to the neutral and the motor stops.

C01RX017

Movement of Intake Actuator

The controller on the automatic heater/air conditioner
control unit selects an intake mode to be used.
As the Terminal No.5 B-26 is grounded via the sliding
contact on the terminal plate, the transistor on the driver
is activated, thus turning on the motor rotation. Then,
accompanying move of the motor, the sliding contact
rotates until grounding of the Terminal No.5 B-26 is

removed, thus stopping the motor.

C01RX006

Overview of Automatic Control of
Automatic Air Conditioner

The automatic heater and air conditioner on this vehicle
has the following features:

• Interior temperature control.

• Air flow control.

• Mode (blow port) control.

• Intake (switching between fresh air and interior air)

control.

• Heater start timing control.

• Cooler start timing control.

• Compressor ON/OFF function according to outside

air temperature level.

• Evaporator anti-freeze control.

Interior Temperature Control

The automatic heater/air conditioner control unit
operates on the setup temperature signal from the
temperature control switch and other sensor signals to
derive the total signal. Then, the control unit compares
this signal against the signal from the potentiometer to
determine rotation direction of the mix actuator. The
mix actuator moves the air mix door to the aperture
specified by the total signal so that the specified interior
temperature is achieved.
If the compressor is turned off in the A/C (air
conditioning) mode, aperture of the air mix door is offset

Conduction pin

Rotation

direction

Remarks

(+) side

(-) side

Clockwise

VENT to DEF

direction

Counter

clockwise

DEF to VENT

direction

Grounding

terminal

Rotation

direction

Remarks

No.5 B-26

Clockwise

RE-CIRCULATI

→

MIX

→

FRE

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