Opel Frontera UE. Manual - part 32

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

5

1

Clockwise

VENT to DEF 

direction

1

5

Counter 

clockwise

DEF to VENT 

direction

Grounding 

terminal

Rotation 

direction

Remarks

No.5 B-26

Clockwise

RE-CIRCULATI

ON

→

MIX

→

FRE

SH

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

1A–101

according to the outside air temperature or the specified
interior temperature.  This function removes the
difference in the blowing temperature in this state and
that of when the compressor is turned on.
When FH or FC is selected for the setup temperature,
the air mix door is accordingly fixed to the Full Heat or
Full Cool mode.
When the VENT mode is selected, aperture of the air
mix door is controlled so that excessively heated air may
not be blown from the VENT blow port.

C01RX011

Air Flow Control

In the Auto Mode

• The automatic heater/air conditioner control unit

operates on the setup temperature signal and other
sensor signals to derive the total signal.  Then, the
control unit adjusts base potential of the power
transistor to match it to the voltage pattern of the
target fan so that stage-less fan speed control can be
achieved.
When solar radiation quantity is detected in the VENT
or B/L mode, the control unit increases the minimum
fan voltage to offset.
When FH or FC is selected from the temperature
control switch, air flow is accordingly fixed to MAX HI
or AUTO HI.

In the Manual Mode

• Air flow specified from the fan switch is entered to the

automatic heater/air conditioner control unit as the
manual signal.  The signal modifies the air flow to the
level specified from the fan switch so that the required
fan voltage is attained.

C01RX010

Mode (Blow Port) Control

The automatic heater/air conditioner control unit
operates on the setup temperature from the control
switch, and temperature and solar radiation quantify
from the sensors to determine the total mode control
signal.  According to the pattern specified by this signal,
the control unit selects either one of the VENT,
BI-LEVEL, FOOT or DEF/FOOT mode.
The mode actuator determines the rotation direction
comparing the target position against the current
position being determined by the position detection
signal.
When FH or FC is selected for the temperature from the
temperature control switch, mode is accordingly fixed to
the VENT or FOOT.

• In the manual operation of the mode switch, you can

select a desired blow port mode pressing the
corresponding mode switch.

1A–102

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

• Operating the DEF mode switch selects the DEF for

the blow port mode.

C01RX009

Intake (Fresh air/interior air switching)
Control

In the Full Auto mode, the automatic heater/air
conditioner control unit operates on the setup
temperature signal and other sensor input signals to
derive the total signal.  According to the pattern
specified by this signal, the control unit provides the
intake control.
When the fan is turned off or the A/C (air conditioning) is
turned off, the intake is fixed to the FRESH mode.
When FC or FH is selected from the control switch, the
intake mode is accordingly fixed to the RECIRC or
FRESH.
In the Manual Operation

• Pressing the FRESH (fresh air intake) or the RECIRC

(room air circulation) accordingly selects the FRESH
or RECIRC mode.

When the DEF Mode Switch is depressed

• The intake mode is fixed to the FRESH.  When the

MANU REC is selected, however, the mode is fixed
the RECIRC.

When the Mode Switch is depressed

• If the automatic intake control is selected, the intake

is fixed to the currently selected mode.

C01RX008

Compressor Control

In the automatic control mode, the automatic heater/air
conditioner control unit turns on or off the compressor
with the evaporator anti-freeze mechanism using the
evaporation sensor.  And, when outside air is detected
to be low through the outside air temperature sensor
signal, the control unit turns off the compressor using
the compressor control function.
Manual Control

• In the automatic control mode, pressing the A/C (air

conditioning) switch turns off the compressor.

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

1A–103

• Pressing the DEF mode switch automatically turns on

the compressor.

C01RX007

Heating Start Timing Control

When the automatic heater/air conditioner is started,
heating is turned on only when the coolant temperature
detected by the coolant temperature sensor is 18

°

C or

less and total signal derived from the sensor signals has
detected that the heating condition is met.
If the coolant temperature detected by the sensor is
18

°

C or less, 4.5V is set for the blower fan motor

terminal voltage and the DEF is selected for the blow
port mode.
When the temperature detected by the sensor is above
18

°

C, the blow port mode is switched to the Auto

Control and the voltage across the blower fan motor
terminal is linearly increased from 4.5V to auto control
voltage (auto airflow).

840RX015

Cooling Start Timing Control

When the automatic heater/air conditioner is started,
cooling is turned on only when the temperature
detected by the interior temperature sensor is 30

°

C or

above and the total signal derived from the sensor
signals has detected that the cooling condition is met.
When the cooling condition has been met, the fan
voltage across the blower fan motor terminal is set to
4.5V for 7 seconds maximum, then it is linearly
increased up to the auto airflow level at the rate of 0.6V/
sec.

C06RX003