heating ISUZU AXIOM 2002 Service Manual PDF

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±69
D01R200009

1A±70
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Functions and Features
Automatic air conditioning control unit
The control unit features a prominent control and display
panel that clearly shows air conditioner operational
settings (delivered air volume, air outlet location,
inside/outside air circulation, and set temperature).
Desired temperature can be set in ±17
C (1
F)
increments. The current setting appears on the digital
display.
Automatic temperature control
Vehicle interior temperature is maintained at the set level.
It is unaffected by changes in vehicle speed, outside air
temperature, and number of passengers.
Maximum cooling and heating
Moving the switch to the 18
C (65
F) position provides
maximum cooling. Moving the switch to the 32
C (90
F)
position provides maximum heating.
Automatic air flow control
Air flow is automatically and precisely regulated in
response to set temperature change and/or changes in
heater unit mixing door aperture.
Automatic air outlet selection
Appropriate air outlets (VENT, BE-LEVEL, FOOT, or
DEF) are selected in response to changes in outlet
temperatures. The mode switch permits manual selection
of the desired air outlet.
Air source (Fresh air intake from outside the
vehicle or recirculation of the air inside the vehicle)
selection
Automatic switching between outside air (FRESH),
recirculated inside air (RECIRC), or a combination of the
two (MIX) occurs in response to changes in outlet
temperatures.The intake switch permits manual
selection of the air source (FRESH or RECIRC). Mixing
of the two sources is not possible during manual
operation. When the defrost mode switch (DEF) is
pressed, the system automatically switches to outside air
intake.
Cooler start-up control
When the vehicle is parked in a hot area for an extended
period of time, the evaporator becomes hot. When the
cooler is turned on, hot air is blown into the vehicle until
the evaporator cools down. The cooler start-up control
prevents blower operation until the evaporator is able to
provide cool air.
Heater start-up control
When the vehicle is parked in a cold area for an extended
period of time, the heater core becomes cold. When the
heater is turned on, cold air is blown into the vehicle until
the heater core heats up. The heater start-up control
prevents blower operation to the air outlets until the
heater core is able to provide warm air. Air is delivered
through the defrost outlets.
Solar radiation offset
The sun sensor uses a photodiode to precisely determine
the amount of solar radiation affecting the vehicle. The
cooler operates in response to this radiation to quickly
correct the vehicle interior temperature.Switch position memory
Current switch positions are stored in memory when the
ignition switch is turned off. When the ignition switch is
turned on again, the switches automatically return to the
position they were in when the ignition switch was turned
off. This simplifies the restarting procedure.
Self-diagnosis function
The self-diagnosis switches on the control panel permit
easy system troubleshooting. Refer to ªSelf-Diagnosisº
later in this Section.

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±71
Automatic Air Conditioner Block Diagram
F01R200004

1A±72
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Control Panel Layout
865R200006
Legend
(1) Temperature Control Switch
(2) Auto Switch
(3) DEF Mode Switch
(4) Rr DEF Mode Switch(5) Intake Switch
(6) Mode Switch
(7) Air Conditioning Switch
(8) Fan Switch
(9) Off Switch

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±73
Air Control Functions
C01R200013
Legend
(1) DEF Door
(2) Air Mix Door
(3) Evaporator Core
(4) Fresh Air Intake
(5) Interior Air Intake
(6) Blower Unit(7) Evaporator Unit
(8) Heater Core
(9) Heater Unit
(10) Sub Air Mix Door
(11) FOOT Door
(12) VENT Door

1A±74
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Control Panel Switch Operation
Switch NamePanel DisplaySwitch Operation
A
u
t
o

S
w
i
t
c
hDuring manual outside air intake (FRESH), pressing the AUTO
switch cancels manual outside air intake. The display panel shows
the current set temperature, the current air outlet(s), and the blower
speed. The intake switch LED shows the current air source. The
A/C switch LED is on.
Air volume, air outlet operation, and air source are controlled
automatically. The compressor is on.
During manual inside air recirculation (REC), pressing the AUTO
switch does not cancel inside air recirculation. The intake switch
LED is on.
O
f
f

S
w
i
t
c
hWhen the OFF switch is pressed, the display panel clears except
for the air outlet indication. Blower and compressor operation stop.
The air source switches from automatic to outside air.
During manual inside air recirculation (REC), pressing the OFF
switch does not cancel inside air recirculation. The intake switch
LED is on.
F
a
n

´


S
w
i
t
c
h
When the fan switch is pressed, air outlet volume (fan speed) can
be manually controlled. Other control switches are unaffected. The
display panel clears AUTO indication.
1. FAN switch is pressed during automatic fan control (AUTO)
Fan control (AUTO)"Press  fan switch"Fan speed increases
from automatic set speed to HI
Fan control (AUTO)"Press
fan switch"Fan speed decreases
from automatic set speed to LO
2. Fan switch is pressed when the fan is off.
Fan (OFF)"Press  fan switch"The fan operates at LO speed
Fan (OFF)"Press
fan switch"The fan operates at LO speed
3. Fan switch is pressed when the fan is in manual operation.
Manual (LO)"Press  fan switch"Manual operation
(LO)" (M1)"(M2)"(M3)"(HI)
Manual (HI)"Press
fan switch"Manual operation
(HI)"(M3)"(M2)"(M1)"(LO)
M
o
d
e

S
w
i
t
c
hPress the mode switch to manually select the air outlet(s). Each
time the switch is pressed, the air outlets change in the progression
shown below.
Mode switch (Automatic control of air
outlets)"VENT"BI-LEVEL"FOOT"DEF/FOOT

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±75
A
/
C
´
S
w
i
t
c
hWhen the A/C switch is pressed, the LED light goes out and the
compressor turns off. If the switch is pressed again, the LED light
turns on and the compressor begins to operate.
The air conditioner will not operate if the fan switch is off.
During manual DEF or D/F operation, the A/C LED will turn on or off
in response to switch operation. However, the compressor remains
on regardless of switch position.
D
E
F

M
o
d
e

S
w
i
t
c
hWhen the defrost switch (DEF) is pressed, air flows from the de-
froster outlets. The compressor is on and blower speed is automati-
cally controlled. Air intake is from outside the vehicle (FRESH). The
defroster symbol appears on the display.
When the defrost switch (DEF) is pressed again, the unit returns to
the settings in use before the defroster was turned on.

1A±76
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
I
Pressing the intake switch permits manual control of air intake and/
or recirculation.
I
n
t
a
k
e

S
w
i
t
c
h
If the intake switch is pressed during manual DEF or D/F, the intake
switch LED briefly turns on. However, outside air intake (FRESH)
continues.
T
e
m
p
e
r
a
t
u
r
e

C
o
n
t
r
o
l
S
w
i
t
c
hThe display panel temperature setting can be set from 18
C (65
F)
to 32
C (90
F).
Pressing and immediately releasing the  switch increases the
temperature setting in -17
C (1
F) increments. If the switch is
pressed and held, the temperature setting increases rapidly.
Pressing and immediately releasing the
switch decreases the
temperature setting in -17
C (1
F) decrements. If the switch is
pressed and held, the temperature setting decreases rapidly.
When the temperature setting is at 32
C (90
F), the unit is set to
maximum heat mode.
When the temperature setting is at 18
C (65
F), the unit is set to
maximum cooling mode.

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±77
Overview of Construction, Movement
and Control of Major Parts of
Automatic Air Conditioner System
Automatic 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 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 right side of meter cluster.
865R200001
Legend
(1) Meter Cluster
(2) In Car Sensor
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
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.
875R200017
Legend
(1) Ambient Sensor
(2) Condenser Assembly
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 ªonº ªoffº 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.
874R200001
Legend
(1) Sensor Part
(2) Duct Sensor Assembly
(3) Evaporator Assembly

1A±78
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 air
conditioner control unit.
This sensor is provided at top of the center cluster upper.
865R200002
Legend
(1) Sun Sensor
(2) Center Cluster Upper
Power Transistor
Receiving base current from the automatic air conditioner
control unit, the power transistor implements stage-less
speed change of the blower fan motor. This transistor is
provided on the evaporator.
874R200009
Legend
(1) Evaporator Assembly
(2) Power Transistor
Max Hi Relay
This relay turned on or off by the signal from the automatic
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.
873RY00005
Legend
(1) Blower Unit
(2) Max High Relay