Isuzu Rodeo UE. Service manual - part 16

1A–34 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Wiring Diagram

D08RX001

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–35

Diagnosis

Air Conditioning Cycle Diagnosis

Condition

Possible cause

Correction

No cooling or insufficient cooling.

Magnetic clutch does not run.

Refer to “Magnetic Clutch Diagnosis”
in this section.

Compressor is not rotating properly.
Drive belt is loosened or broken.

Adjust the drive belt to the specified
tension or replace the drive belt.

Compressor is not rotating properly.
Magnetic clutch face is not clean and
slips.

Clean the magnetic clutch face or
replace.

Compressor is not rotating properly.
Incorrect clearance between
magnetic drive plate and pulley.

Adjust the clearance. Refer to
Compressor in this section.

Compressor is not rotating properly.
Compressor oil leaks from the shaft
seal or shell.

Replace the compressor

Compressor is not rotating properly.
Compressor is seized.

Replace the compressor

Insufficient or excessive charge of
refrigerant.

Discharge and recover the
refrigerant.  Recharge to the
specified amount.

Leaks in the refrigerant system.

Check the refrigerant system for
leaks and repair as necessary.
Discharge and recover the
refrigerant.  Recharge to the
specified amount.

Condenser is clogged or insufficient
radiation.

Clean the condenser or replace as
necessary.

Temperature control link unit of the
heat unit is defective.

Repair the link unit.

Unsteady operation due to a foreign
substance in the expansion valve.

Replace the expansion valve.

Poor operation of the electronic
thermostat.

Check the electronic thermostat and
replace as necessary.

Insufficient velocity of cooling air.

Evaporator clogged or frosted.

Check the evaporator core and
replace or clean the core.

Air leaking from the cooling unit or air
duct.

Check the evaporator and duct
connection, then repair as
necessary.

Blower motor does not rotate
properly.

Refer to Fan Control Lever (Fan
Switch) Diagnosis in this section.

*For the execution of the charging and discharging
operation in the table above, refer to Recovery,
Recycling, Evacuating and Charging in this section.

1A–36 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Checking The Refrigerant System With
Manifold Gauge

Since Refrigerant-134a (HFC-134a) is used in the air
conditioning system in this vehicle, be sure to use
manifold gauges, charging hoses and other air
conditioning service tools for HFC-134a when
checking the refrigerant system.

Conditions:

f

Run the engine at Idling

f

Air conditioning switch is “ON”

f

Run the blower motor at “HIGH” position

f

Temperature control lever set to “MAX COLD”

f

Air source selector lever at “CIRC”

f

Open the engine hood

f

Close all the doors

Normal Pressure:

f

At ambient temperature: approx. 25–30

°

C

(77–86

°

F).

f

At low-pressure side: approx. 147.1–294.2 kPa
(21.3–42.7 psi).

f

At high-pressure side: approx. 1372.9–1863.3 kPa
(199.1–270.2 psi).

Refer to the table on the refrigerant pressure-temperature
relationship.

HFC-134a Pressure-Temperature Relationship

Pressure

Temperature

(kPa)

(psi)

(

°

C)

(

°

F)

36

5.3

–20

–4.4

67

9.7

–15

5

104

15

–10

14

147

21

–5

23

196

28

0

32

255

37

5

41

314

45

10

50

392

57

15

59

471

68

20

68

569

82

25

77

677

98

30

86

785

114

35

95

912

132

40

104

1059

154

45

113

1216

176

50

122

Connect The Manifold Gauge
Low-pressure hose (LOW) — Suction side
High pressure hose (HI) — Discharge side

901RS180

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–37

Legend

(1) Low Side
(2) High Side

Condition

Possible cause

Correction

Discharge (High Gauge) Pressure
Abnormally High

Condenser clogged or dirty.

Clean the condenser fins

Abnormally High

Cooling fan does not operate
properly.

Check the cooling fan operation.

Discharge (High Gauge) Pressure
Abnormally High.
Insufficient cooling.

Excessive refrigerant in system.

Discharge and recover refrigerant.
Recharge to specified amount.

Discharge (High Gauge) Pressure
Abnormally High.
High pressure gauge drop. (After
stopping A/C, the pressure drops
approx. 196 kPa (28 psi) quickly)

Air in system.

Evacuate and charge refrigerant
system.

Discharge (High Gauge) Pressure
Abnormally Low.
Insufficient cooling

Insufficient refrigerant in system.

Check for leaks. Discharge and
recover the refrigerant. Recharge to
the specified amount.

Discharge (High Gauge) Pressure
Abnormally Low.
Low pressure gauge indicates
vacuum.

Clogged or defective expansion
valve.

Replace the expansion valve.

Discharge (High Gauge) Pressure
Abnormally Low.
Frost or dew on refrigerant line
before and after the receiver/drier or
expansion valve, and low pressure
gauge indicates vacuum.

Restriction caused by debris or
moisture in the receiver/drier.

Check system for restriction and
replace the receiver/drier.

Discharge (High Gauge) Pressure
Abnormally Low.

Compressor seal defective

Repair or replace the compressor.

High and low pressure gauge
balanced quickly. (After turned off
A/C)

Poor compression due to a defective
compressor gasket.

Repair or replace the compressor.

Suction (Low Gauge) Pressure
Abnormally High.
Low pressure gauge (Low pressure
gauge is lowered after condenser is
cooled by water.)

Excessive refrigerant in system.

Discharge and recover refrigerant
Recharge to specified amount.

Suction (Low Gauge) Pressure
Abnormally High.
Low pressure hose temperature.
(Low pressure hose temperature
around the compressor refrigerant

Unsatisfactory valve operation due
to  defective temperature sensor of
expansion valve.

Replace the expansion valve.

around  the  com ressor  refrigerant
line connector is lower than around
evaporator.)

Expansion valve opens too long.

Replace the expansion valve.

Suction (Low Gauge) Pressure
Abnormally High.
High and low pressure gauge
balanced quickly. (After turned off
A/C)

Compressor gasket is defective.

Repair or replace the compressor.

Suction (Low Gauge) Pressure
Abnormally Low.
Insufficient cooling.

Insufficient refrigerant in system.

Check for leaks. Discharge and
recover the refrigerant. Recharge to
specified amount.