Isuzu Trooper (2000 year). Manual - part 33

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–101

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

D

In the automatic control mode, pressing the A/C (air
conditioning) switch turns off the compressor.

D

Pressing the DEF mode switch automatically turns on
the compressor.

C01RY00010

Heating Start Timing Control

When the automatic heater/air conditioner is started,
heating is turned on under following conditions.

D

The detected temperature of thermo unit is 136

°

F or

less.

D

The temperature setting signal and the total signal by
each sensor meet the condition of heating.

When the detected temperature by the coolant
temperature sensor is 136

°

F or less, the blower fan motor

is set to work at low speed and the “DEF” mode is
selected.
When the detected temperature by the coolant
temperature sensor is 77

°

F or more, the blow mode

changes automatic control. And the blower fan speed is
controlled to be lineally up from “LO” to “MAX HI”.

840RY00018

Cooling Start Timing Control

When the automatic heater/air conditioner is started,
cooling is turned on under following conditions.

D

The in car sensor is 86

°

F or more.

D

The temperature setting signal and the signals from
each sensor meet the specified condition.

The blower fan speed is set to “LO” for maximum 7
seconds when cooling start conditions meet, and then, is
controlled to be lineally up to “MAX HI” by 5.32%/S.

C06RY00001

1A–102 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Troubleshooting

Troubleshooting, Its Overview and
Procedures

The full automatic heater and air conditioner equips with
the “Self-Diagnosis Function” 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 “Checking Procedures by Failed
Location”.  As for a location this function is unappreciable,
the system accurately determines characteristics of a
given trouble and checks relevant parts according to the
“Checking Procedures by Failed Location”.
The following illustrates basic troubleshooting flow.

Basic Troubleshooting Flow

F01RX009

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–103

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.

D08RY00138

Condition

Possible cause

Correction

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

—

Refer to Chart A

1A–104 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–16 normal?

—

Go to Step 2

Replace the

fuse

2

Is the fuse C–20 normal?

—

Go to Step 3

Replace the

fuse

3

Disconnect the auto A/C control unit connector I–32.

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–16 and
terminal No.I32–8.

Is the action complete?

—

Go to Step 4

—

5

Is there continuity between the harness side connector
terminal No.I33–16 and the ground?

—

Go to Step 7

 Go to Step 6

6

Repair an open circuit between terminal No.I33–16 and
the ground No.B–2.

 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.I32–10 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.I32–10.

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.I32–7 and the ground?

Approx. 12V

—

Go to Step 10

10

Repair an open circuit between the fuse C–20 and
terminal No.I32–7.

Is the action complete?

—

Verify repair

—