ISUZU AXIOM 2002 Service Repair Manual

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±85
Compressor Control
In the automatic control mode, the automatic 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.

Pressing the DEF mode switch automatically turns on
the compressor.
C01R200002
Heater Start-up Control
Heater start-up control occurs when the air discharge
mode is in the BI=LEVEL, FOOT, or DEF/FOOT position
and the heater core temperature is less than 14
C (58
F).
Air discharge volume remains in the AUTO LO mode until
the engine coolant temperature rises above 14
C (58
F).
The volume then increases in linear increments to the
pre-set level.
840R200010
Cooler Start-up Control
When cooler operation is started with the air discharge
mode is in the VENT or B/L position and the in-car
temperature higher than 26
C (78
F) (detected by the
in-car sensor), cooler start-up control occurs.
For the first 7 seconds of cooler operation, the fan
remains OFF. It then switches to AUTO LO. Air discharge
volume then increases in linear increments to the pre-set
level.
Cooler start-up control occurs the first time the engine is
started or the cooler switch is moved from OFF to AUTO.
It will not occur during subsequent switch movements.
C06R200001

1A±86
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Troubleshooting
Troubleshooting, Its Overview and
Procedures
The automatic air conditioner equips with the
ªSelf-Diagnosis Functionº to check its major components.
This function makes access to the sensors, actuators and
blower fan motor system easier when checking them up
and, when a failed part is located, this function restores its
original performance.When implementing the troubleshooting, this
self-diagnosis function narrows the range to be searched
at the first step, then check relevant parts one by one
according to the ªChecking Procedures by Failed
Locationº. As for a location this function is unappreciable,
the system accurately determines characteristics of a
given trouble and checks relevant parts according to the
ªChecking Procedures by Failed Locationº.
The following illustrates basic troubleshooting flow.
Basic Troubleshooting Flow
F01RX009

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±87
Auto Air Conditioner Control Unit Power Supply Diagnosis
This check is required because a trouble on the auto
amplifier (control unit) power supply circuit or grounding
circuit prevents accurate troubleshooting.
D08R200034
ConditionPossible causeCorrection
Power source does not supply to
auto air conditioner control unit.ÐRefer to Chart A

1A±88
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Chart ªAº: Check of Auto Amplifier Power Supply System
StepActionValue(s)Ye sNo
1Is the fuse C±5 normal?
ÐGo to Step 2
Replace the
fuse
2Is the fuse F±7 normal?
ÐGo to Step 3
Replace the
fuse
3Disconnect the auto A/C control unit connector I±19.
Is the battery voltage applied between the harness side
connector terminal No.I32±8 and the ground?
Approx. 12VGo to Step 5Go to Step 4
4Repair an open circuit between the fuse C±5 and
terminal No.I19±8.
Is the action complete?
ÐGo to Step 4Ð
5Is there continuity between the harness side connector
terminal No.I19±16 and the ground?
ÐGo to Step 7 Go to Step 6
6Repair an open circuit between terminal No.I19±16 and
the ground No.B±9.
Is the action complete?
ÐGo to Step 5Ð
7Turn the lighting switch on.
Is the battery voltage applied between the harness side
connector terminal No.I19±12 and the ground?
Approx. 12VGo to Step 9Go to Step 8
8Repair an open circuit between the lighting switch and
terminal No.I19±12.
Is the action complete?
ÐGo to Step 7Ð
9Turn the starter switch on.
Is the battery voltage applied between the harness side
connector terminal No.I19±7 and the ground?
Approx. 12VÐGo to Step 10
10Repair an open circuit between the fuse F±7 and
terminal No.I19±7.
Is the action complete?
ÐVerify repairÐ

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±89
Performance and Movement
checklist for Automatic Air
Conditioner Related Parts
Start the engine, and when the engine coolant reached
50
C (122
F) check performance and movement of the
related parts according the following checklist.
Performance Check Using the Manual Switch
NoItemProcedureCriteriaNo.ItemConditionOperationCriteria
1
Air discharge
temperature
(Ai i d
Auto±switch ONSet temperature to
18
C (65
F).Cold air discharge.
1(Air±mix door
operation)Set temperature to
32
C (90
F).Hot air discharge.
2
Air discharge
volume (Fan
operation)Fan switch ON1. Set temperature to
25
C (77
F).
2. Press the OFF
switch.Fan does not operate. There is no
air discharge.
21. Set temperature to
25
C (77
F).
2. Press the fan 
switch.Fan operates. Fan speed increases
each time the switch is pressed (LO
to HI in 5 increments).
3
Air discharge
temperature
(Mode door
operation)Fan in manual
5±speed operation1. Set temperature to
25
C (77
F).
2. Press the mode
switch.
3. Move through the 5
modes
(VENT"BI±LEVEL
"FOOT"DEF/FO
OT"DEF).
Panel display lights for each
mode.

Air discharge outlet position
changes for each mode.
4
Inside/outside air
mode (Intake door
operation)Auto±switch ON1. Set temperature to
25
C (77
F).
2. Press the intake
switch.
3. Press the fan 
switch.
4. Set the fan to the
highest speed.
5. Press the intake
switch.
Intake switch LED turns from on
to off.

Air discharge sound changes.
5
CompressorOutside air
temperature above
0
C (32
F) and
vehicle interior at
normal temperature1. Set temperature to
25
C (77
F).
2. Press the OFF
switch.
3. Press the
auto±switch.
4. Press the air
conditioner switch.
When the auto±switch is
pressed, the LED in the air
conditioner switch turns on and
the compressor begins
operation.

When the air conditioner switch
is pressed, the LED in the air
conditioner switch turns off and
the compressor stops operation.

1A±90
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Check of Auto Function
NoItemProcedureCriteriaNo.ItemConditionOperationCriteria

AUTO display highlighted on
display panel.

Cold air discharge.
Set temperature to
18
C (65
F)

VENT mode.
18C (65F).
Intake switch LED on.

Fan speed bar graph display at
MAX6dash;HI

A/C switch LED on.
1Automatic operationAuto-switch ON
Gradually increase
the temperature
setting from 18
C
(65
F) to 31.5
C
(89
F).

Temperature of air discharge
increases with increase in setting
temperature.

Air discharge volume changes.

Panel display shows VENT,
BI±LEVEL, FOOT, or DEF/FOOT.

Hot air discharge.

A/C bar graph display disappears.
Set temperature to
32
C (90
F)

Foot mode.
32
C (90
F).
Intake LED switch off.

Fan speed bar graph display at
MAX-HI

A/C switch LED on.

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±91
Troubleshooting With Self-Diagnosis Function
Overview of Self-Diagnosis Function
Sensors (input) and actuators (output) are used to check
circuit function and provide essential data on these
circuits. For more detailed information, refer to the
[Inspection and Repair] Sections for the applicable
system or component.
The Table below shows how to turn the self-diagnosis
function on and off.
Self-Diagnosis Operation Procedure
865R200033

1A±92
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
StepActionValue(s)Ye sNo
11. Allow the engine to idle until it completely warms up.
2. Turn the starter switch to the OFF position.
3. Place a 60±watt lamp approximately 15 cm from the
sun sensor.
NOTE: This procedure is best performed at night or in
a dark, unlit area.
Is the action complete?
ÐGo to Step 2Ð
2Simultaneously press and hold the RESET key and the
CLOCK key (display unit).
Move the starter switch to start the engine.
Does DIAG appear on the display?
ÐGo to Step 3
Replace
display unit
3Press the COMPUTER MODE key.
Does DIAG AIRCON appear on the display?
ÐGo to Step 4
Replace
audio unit
4NOTE: A '1' should appear in the set temperature
segment of the display.
Does '0' appear in the outside air segment of the
display?
ÐGo to Step 6Go to Step 5
5Repair or replace damaged parts.
NOTE: Refer to
Step 1 Trouble Code Table.
Is the action complete?ÐGo to Step 1Ð
6Press and release the  fan switch (one time only).
NOTE: A '2' should appear in the set temperature
segment of the display.
Does '0' appear in the outside air segment of the
display?
ÐGo to Step 8Go to Step 7
7Repair or replace damaged parts.
NOTE: Refer to
Step 2 Trouble Code Table.
Is the action complete?ÐGo to Step 1Ð
8Press and release the  fan switch (one time only).
NOTE:

Refer to
Step 3 Sensor Output Check for a sample
output value.

A '3' should appear in the set temperature
segment of the display.
Does the correct sensor output value appear in the
outside air segment of the display?
ÐGo to Step 10Go to Step 9
9Repair or replace damaged parts.
NOTE: Refer to
Trouble Spot Inspection.
Is the action complete?ÐGo to Step 1Ð
10Press and release the  fan switch one time only.
NOTE: Refer to
Step 4 (Operation Check) for display
readings and inspection steps.
Are all parts operating normally?
ÐGo to Step 12Go to Step 11

HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
1A±93
StepNo Ye s Value(s) Action
11Repair or replace damaged parts.
NOTE: Refer to
Trouble Spot Inspection.
Is the action complete?ÐGo to Step 1Ð
121. Press and release the
fan switch (one time only).
2. Press the DEF switch several times.
NOTE: A '3' should appear in the set temperature
segment of the display.
Does the correct sequence pattern (1, 2, 1, 2) appear in
the outside air segment of the display?
ÐGo to Step 15Go to Step 13
13Perform diagnosis for DEF switch, intake actuator, and
AUTO A/C control unit.
Have the diagnosis procedures been completed.
ÐGo to Step 14Ð
141. Press and release the
fan switch (one time only).
2. Press the DEF switch several times.
Are all parts operating normally?
ÐGo to Step 15
Replace
display unit
15Turn the starter switch OFF.
Is the action complete?
ÐÐÐ

1A±94
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
STEP 1: Trouble Code Table
Trouble
CodeDefective PartTrouble
CodeDefective Part
1In Car Sensor Open Circuit± 1In Car Sensor Short Circuit
2Ambient Sensor Open Circuit± 2Ambient Sensor Short Circuit
3Sun Sensor Open Circuit± 3Sun Sensor Short Circuit
4Duct Sensor Open Circuit± 4Duct Sensor Short Circuit
5Mix Potentiometer Open Circuit± 5Mix Potentiometer Short Circuit
6Mode Encoder Open Circuit
7Intake Encoder Open Circuit
0No Defective Part
STEP 2: Trouble Code Table
Trouble
CodeDefective PartTrouble
CodeDefective Part
1In Car Sensor Open Circuit± 1In Car Sensor Short Circuit
2Ambient Sensor Open Circuit± 2Ambient Sensor Short Circuit
3Not Used± 3Sun Sensor Short Circuit
4Duct Sensor Open Circuit± 4Duct Sensor Short Circuit
5Mix Potentiometer Open Circuit± 5Mix Potentiometer Short Circuit
6Mode Encoder Open Circuit
7Intake Encoder Open Circuit
0No Defective Part