Isuzu Trooper (2000 year). Service manual - part 19

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–45

The air conditioning can be stopped by turning off the air
conditioning switch or the fan control knob (fan switch).
However, even when the air conditioning is in operation,
the electronic thermostat, the pressure switch or the
Powertrain Control Module (PCM) is used to stop the air
conditioning temporarily by turning off the magnetic clutch

in the prearranged conditions to reduce the engine load
which is being caused by the rise in the engine coolant
temperature, and the acceleration of the vehicle, etc.
For the inspection of the relays, switches and units in the
table, refer to “Individual Inspection” in this section.

Magnetic Clutch Does Not Run

Step

Action

Yes

Are No. C-20 (10A) fuse and No. C-19 (25A) fuse OK?

Go to Step 2

Replace

Are heater and A/C (B-36), thermostat (X-5), and compressor
(X-7) relays OK?

Go to Step 3

Replace

Is pressure switch (dual pressure switch) OK?

Go to Step 4

Switch defective

or insufficient

refrigerant.

Are air conditioning switch and fan control knob (Fan Switch) OK?

Go to Step 5

Replace

1. Turn the ignition switch “ON” (Engine is running).
2. Air conditioning switch and fan control knob (Fan Switch)

“ON”.

3. Check to see if battery voltage is present at chassis side

connector terminal No. E3-1.

Is there a battery voltage?

Go to Step 6

Go to Step 7

Check to see if continuity between compressor side connector
terminal No. E3-1 and the magnetic clutch side connector
terminal.

Is there a continuity?

Magnetic clutch

defective.

Compressor

defective.

Check to see if battery voltage is present at chassis side
connector terminal No. C25-1

Is there a battery voltage?

Go to Step 8

Open circuit

between No.C-20

(10A) fuse and

No. C25-1.

1. Disconnect thermostat relay (X-5).
2. Check to see if battery voltage is present at the chassis side

relay terminal NO. X5-2

Is there a battery voltage?

Go to Step 9

Open circuit

between No.

C25-2 and

No.X5-2.

Check to see if voltage (approx. 10V) is present between chassis
side relay terminal No. X5-1 and No. X5-3.

Is there a battery voltage?

Go to Step 10

Go to Step 16

1. Reconnect thermostat relay and disconnect compressor relay

(X-7).

2. Check to see if battery voltage is present at the chassis side

relay terminal No. X7-2.

Is there a battery voltage?

Go to Step 11

Open circuit

between No.

X5-4 and No.

X7-2.

Check to see if continuity between chassis side relay terminal No.
X7-4 and the chassis side connector terminal No. E3-1.

Is there a continuity?

Go to Step 12

Open circuit.

Check to see if battery voltage is present between chassis side
relay terminal No. X7-1 and No. X7-3.

Is there a battery voltage?

Go to Step 13

Go to Step 14

Check to see if battery voltage is present at chassis side relay
terminal No. X7-1.

Is there a battery voltage?

Go to Step 15

Open circuit

between No.

C-20 (10A) fuse

and No. X7-1.

1A–46 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Magnetic Clutch Does Not Run (Cont’d)

Step

Yes

Action

Check to see if battery voltage is present at chassis side
connector terminal No. C1-B14.

Is there a battery voltage?

Power train

control module

(PCM) defective.

Refer to

Driveability and

Emissions in

Engine section.

Open circuit

between No.

X7-3 and No.

C1-B14.

Check to see if continuity between chassis side relay terminal No.
X-54 and chassis side connector terminal No. C3-E15.

Is there a continuity?

Power train

control module

(PCM) defective.

Refer to

Driveability and

Emissions in

Engine section.

Open circuit

Check to see if battery voltage is present at chassis side relay
terminal No. X5-1.

Is there a battery voltage?

Go to Step 17

Go to Step 20

1. Reconnect thermostat relay.
2. Check to see if battery voltage is present at chassis side

connector terminal No. B4-3.

Is there a battery voltage?

Go to Step 18

Open circuit

between No.I23-6

and No.B4-3.

Check to see if battery voltage (appox 10V) is present at chassis
side connector terminal No. B4-1.

Is there a battery voltage?

Go to Step 19

Open circuit

between No.

X5-3 and No.

B4-1.

Check to see if continuity between chassis side connector
terminal No. B4-2 and No. I18-4.

Is there a continuity?

Electronic

thermostat

defective.

Open circuit

between No.

B4-2 and No.

I18-4 or poor

ground (Fan

Switch Ground

Circuit).

Check to see if battery voltage is present at chassis side
connector terminal No. I23-2.

Is there a battery voltage?

Open circuit

between X5-1

and No.I23-6.

Open circuit

between No.

C-20 (10A) fuse

and No.I23-2.

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–47

Individual Inspection

Fan Control Knob (Fan Switch) And Air
Conditioning (A/C) Switch

1. Check for continuity between the fan switch and the

A/C switch side connector terminals.

865RS002

Fan swtich

position

Fan switch connector terminals with

continuity

OFF

No continuity

1 – 2 – 4

1 – 4 – 5

1 – 3 – 4

1 – 4 – 6

A/C switch

position

A/C switch connector terminals with

continuity

OFF

1 – 6

1 – 2 – 6

Heater And A/C (B-36), Thermostat (X-5)
And Compressor (X-7) Relay

1. Disconnect relays and check for continuity and

resistance between relay terminals.

For handling of these relays, refer to Heater &A/C
Relay in this section.

825RS003

Condition

Relay terminals with

continuity

Normal

1 – 3 (Approx 85–105

)

When battery voltage is

applied between 1 – 3

2 – 4

1A–48 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Pressure Switch

1. Disconnect pressure switch connector and check for

continuity between pressure switch side connector
terminals (1) and (2).

875RW003

General Repair Procedure

Precautions For Replacement or Repair of
Air Conditioning Parts

There are certain procedures, practices and precautions
that should be followed when servicing air conditioning
systems:

Keep your work area clean.

Always wear safety goggles and protective gloves
when working on refrigerant systems.

Beware of the danger of carbon monoxide fumes
caused by running the engine.

Beware of discharged refrigerant in enclosed or
improperly ventilated garages.

Always disconnect the negative battery cable and
discharge and recover the refrigerant whenever
repairing the air conditioning system.

When discharging and recovering the refrigerant, do
not allow refrigerant to discharge too fast; it will draw
compressor oil out of the system.

Keep moisture and contaminants out of the system.
When disconnecting or removing any lines or parts,
use plugs or caps to close the fittings immediately.
Never remove the caps or plugs until the lines or parts
are reconnected or installed.

When disconnecting or reconnecting the lines, use
two wrenches to support the line fitting, to prevent
from twisting or other damage.

Always install new O-rings whenever a connection is
disassembled.

Before connecting any hoses or lines, apply new
specified compressor oil to the O-rings.

When removing and replacing any parts which
require discharging the refrigerant circuit, the
operations described in this section must be
performed in the following sequence:

1. Use the J-39500 (ACR

: HFC-134a Refrigerant

Recovery / Recycling / Recharging / System) or
equivalent to thoroughly discharge and recover the
refrigerant.

2. Remove and replace the defective part.
3. After evacuation, charge the air conditioning

system and check for leaks.

Repair Of Refrigerant Leaks

Refrigerant Line Connections
Install new O-rings, if required. When disconnecting or
connecting lines, use two wrenches to prevent the
connecting portion from twisting or becoming damaged.

852RS003

When connecting the refrigerant line at a block joint,
securely insert the projecting portion of the joint portion
into the connecting hole on the unit side and secure with a
bolt. Apply the specified compressor oil to the O-rings
prior to connecting.

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