Isuzu N-Series. Manual - part 62

1B-18 AIR CONDITIONING

1. Make sure the evacuation process is correctly

completed.

2. Connect the center-hose of the manifold gauge to

the refrigerant container.

• Turn the charge valve handle counterclockwise to

purge the charging line and purge any air existing
in the center-hose of the manifold gauge.

3. Open the low-pressure hand valve and charge the

refrigerant about 200 g (0.44 lbs.).

• Make sure the high-pressure hand valve is closed.
• Avoid charging the refrigerant by turning the refrig-

erant container upside down.

4. Close the low-pressure hand valve of the manifold

gauge.

• Check to ensure that the degree of pressure does

not charge.

5. Check the refrigerant leaks by using a R-134a leak

detector.

• If a leak occurs, repair the leak connection, and

start all over again from the first step of evacuation.

6. If no leaks are found, open the low-pressure hand

valve of the manifold gauge. Then continue charg-
ing refrigerant to the system.

• When charging the system becomes difficult:

1) Run the engine at 1,300 — 1,500 rpm and open

the all vehicle doors.

2) A/C switch is “ON”.
3) Set the fan control knob (fan switch) to its high-

est position.

Warning:

WARNING:

BE ABSOLUTELY SURE NOT TO OPEN THE HIGH-
PRESSURE HAND VALVE. SHOULD THE HIGH-
PRESSURE HAND VALVE BE OPENED, THE HIGH-
PRESSURE REFRIGERANT GAS WOULD FLOW
BACKWARD, AND THIS MAY CAUSE THE REFRIG-
ERANT CONTAINER TO BURST.

7. When the refrigerant container is emptied, use the

following procedure to replace it with a new refrig-
erant container.
1) Close the low pressure hand valve.
2) Raise the needle upward and remove the

charge valve.

3) Reinstall the charge valve to the new refriger-

ant container.

4) Purge any air existing in the center hose of the

manifold gauge.

8. Charge the system to the specified amount and

then close the low-pressure hand valve.

• A fully charged system is indicated by the sight

glass on the receiver/drier being free of any bub-
bles (Refer to “Reading Sight Glass”).

• Check the high and low pressure value of the man-

ifold gauge.

• Check for refrigerant leaks by using a R-134a leak

detector.
Immediately after charging refrigerant, both high
and low pressures are slightly high and to the left
of the gauge, but they settle down to the guide
pressure valves as shown below:

• Ambient temperature; 30 — 35

°C (86 — 95°F)

• Guide pressure

High-pressure side;
Approx. 1373 — 1667 kPa (14 — 17 kg/cm

2

 / 199

— 242 PSI)
Low-pressure side;
Approx. 127 — 245 kPa (1.3 — 2.5 kg/cm

2

 / 18 —

36 PSl)

9. Close the low pressure hand valve and charge

valve of the refrigerant container.

10. Stop the air conditioning and the engine.
11. Disconnect the high and low pressure hoses from

the manifold gauge fittings.

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Refrigerant Amount

g (lbs.)

450 (0.99) GCC, 600 (1.32) Australia & Taiwan

AIR CONDITIONING 1B-19

Reading Sight Glass

The sight glass provides accurate diagnosis only under
the following conditions.
If the vehicle can be tested under these conditions,
check the sight glass appearance and compare to the
chart.

• Engine speed 1,500 RPM
• A/C switch “ON”
• Blower fan operating at highest speed
• Air source selector lever at “RECIRC”
• Temperature control knob at coldest position
• Ambient temperature below 35

°C (95°F) and hu-

midity below 70%

Notice:

If the vehicle cannot be moved to a testing location that
meets these specifications, then the sight glass cannot
be used for diagnosis. You must discharge and recover
the refrigerant, then recharge the system with the spec-
ified amount of refrigerant. Then continue checking the
system performance.

• High side pressure less than 1667 kPa (17 kg

⋅cm

2

/ 242 PSI) 

Notice:

If the high side pressure is greater than stated, the sight
glass cannot be used for diagnosis. You must discharge
and recover the refrigerant, then recharge the system
with the specified amount of refrigerant.
Then continue checking system performance.

High 
and low 
pres-
sure 
pipe 
temper-
ature

The high pressure pipe 
is hot and the low pres-
sure pipe is cold. There 
is a distinct difference in 
temperature between 
them.

The high pressure pipe 
is warm and the low 
pressure pipe is cool. 
There is no great differ-
ence in temperature 
between them.

There is little difference 
in temperature between 
the high pressure pipe 
and the low pressure 
pipe.

The high pressure pipe 
is hot and the low pres-
sure pipe is slightly 
warm. There is a differ-
ence in temperature 
between them.

Sight 
glass 
condi-
tion

Almost transparent. A 
flow of bubbles can be 
seen, but they disap-
pear when the throttle is 
opened.

A flow of bubbles 
always can be seen. It 
appears sometimes 
transparent, and some-
times frothy.

Something like fog 
faintly can be seen.

Even at idle with the fan 
at “HI” (with the window 
fully open), the bubbles 
cannot be seen.

Air con-
ditioner 
cycle 
condi-
tion

OK

NG

(Not enough refrigerant)

NG

(Almost no refrigerant)

NG

(Too much refrigerant)

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1B-20 AIR CONDITIONING

Compressor

Removal

Preparation:
Disconnect the battery ground cable.
Discharge and recover refrigerant.

1. Magnetic clutch harness connector
2. Drive Belt

Loosen the tension pulley center nut (1) and ten-
sion adjustment bolt (2), then remove the drive belt
(3).

Legend

1. Magnetic clutch harness connector

4. Compressor

2. Drive belt

5. O-ring

3. Refrigerant line

5

3

1

2

4

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AIR CONDITIONING 1B-21

3. Refrigerant line

When removing the line connector, the connecting
part should immediately be plugged or capped to
prevent foreign matter from being mixed into the
line.

4. Compressor

Installation

1. Compressor

Tighten the compressor fixing bolts to the specified
torque.

Tighten:

Compressor Bolt to 19 N

⋅m (1.9 kg⋅m/14 lb⋅ft).

2. Refrigerant Line

• Tighten the refrigerant line fixing bolt to the speci-

fied torque.

Tighten:

Refrigerant Line Bolt to 27 N

⋅m (2.8 kg⋅m/20 lb⋅ft).

• O-ring cannot be reused. Always replace with new

ones.

• Be sure to apply new specified compressor oil to

the O-rings when connecting refrigerant lines.

3. Drive Belt

Push the drive belt with the force of 10 kg (22 lbs)
and adjust the drive belt tension by tightening idle
pulley tension adjustment bolt, until the 8 — 12 mm
(0.31 — 0.47 in) deflection of the belt is obtained.
Then tighten the pulley center nut.

Tighten:

Idle Pulley Center nut to 39 N

⋅m (4.0 kg⋅m/29 lb⋅ft).

4. Magnetic Clutch Harness Connector

New Compressor Installation

The new compressor is filled with 180cc (5.0 lmp fl oz)
of compressor oil and nitrogen gas. When mounting the
compressor on the vehicle, perform the following steps;

1. Gently release nitrogen gas from the rear head of

the new compressor.

• Take care not to let the compressor oil flow out.
• Inspect O-rings and replace if necessary.

2. Turn the compressor several times by hand and re-

lease the compressor oil in the cylinder.

3. When installing on a new system, the compressor

should be installed as it is. When installing on a
used system, the compressor should be installed
after adjusting the amount of compressor oil. (Re-
fer to Section 1D “COMPRESSOR OVERHAUL”
for General Information.)

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Legend

1. A/C compressor
2. Pulley
3. Center nut
4. Drive belt
5. Adjustment bolt
6. Crank pulley
7. Tension pulley
8. Generator

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