Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual - part 29

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

Condition

Possible cause

Correction

Power source does not supply to
auto air conditioner control unit.

—

Refer to 

Chart A

1A–88 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Chart “A”: Check of Auto Amplifier Power Supply System 

Step

Action

Value(s)

Yes

No

1

Is the fuse C–5 normal?

—

Go to 

Step 2

Replace the

fuse

2

Is the fuse F–7 normal?

—

Go to 

Step 3

Replace the

fuse

3

Disconnect 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. 12V

Go to 

Step 5

Go to 

Step 4

4

Repair an open circuit between the fuse C–5 and
terminal No.I19–8.

Is the action complete?

—

Go to 

Step 4

—

5

Is there continuity between the harness side connector
terminal No.I19–16 and the ground?

—

Go to 

Step 7

 Go to 

Step 6

6

Repair an open circuit between terminal No.I19–16 and
the ground No.B–9.

Is the action complete?

—

Go to 

Step 5

—

7

Turn the lighting switch on.

Is the battery voltage applied between the harness side
connector terminal No.I19–12 and the ground?

Approx. 12V

Go to 

Step 9

Go to 

Step 8

8

Repair an open circuit between the lighting switch and
terminal No.I19–12.

Is the action complete?

—

Go to 

Step 7

—

9

Turn the starter switch on.

Is the battery voltage applied between the harness side
connector terminal No.I19–7 and the ground?

Approx. 12V

—

Go to 

Step 10

10

Repair an open circuit between the fuse F–7 and
terminal No.I19–7.

Is the action complete?

—

Verify repair

—

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

No

Item

Procedure

Criteria

No.

Item

Condition

Operation

Criteria

1

Air discharge
temperature
(Ai

i d

Auto–switch ON

Set 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 ON

1. Set temperature to

25

°

C (77

°

F).

2. Press the OFF

switch.

Fan does not operate. There is no
air discharge.

2

1. 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 operation

1. 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).

D

Panel display lights for each
mode.

D

Air discharge outlet position
changes for each mode.

4

Inside/outside air
mode (Intake door
operation)

Auto–switch ON

1. 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.

D

Intake switch LED turns from on
to off.

D

Air discharge sound changes.

5

Compressor

Outside air
temperature above
0

°

C (32

°

F) and

vehicle interior at
normal temperature

1. Set temperature to

25

°

C (77

°

F).

2. Press the OFF

switch.

3. Press the

auto–switch.

4. Press the air

conditioner switch.

D

When the auto–switch is
pressed, the LED in the air
conditioner switch turns on and
the compressor begins
operation.

D

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

No

Item

Procedure

Criteria

No.

Item

Condition

Operation

Criteria

AUTO display highlighted on
display panel.

Cold air discharge.

Set temperature to
18

°

C (65

°

F)

VENT mode.

18 C (65 F).

Intake switch LED on.

Fan speed bar graph display at
MAX6dash;HI

A/C switch LED on.

1

Automatic operation

Auto-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.