air conditioning ISUZU TF SERIES 2004 Workshop Manual

1-78 HEATER AND AIR CONDITIONING


RTW4A0SH000201

Pressure switch
Disconnect pressure switch connector and check for continuity
between pressure switch side connector terminal.


825r300045


Heater and thermo switch relay.
Check for continuity between the relay terminals.

1 - 5





No continuity
(When battery voltage is applied between 2 - 4 )
1 - 5





Continuity
825r300023

Check for continuity between the relay terminals.
1 - 2





No continuity
(When battery voltage is applied between 3 - 4 )
1 - 2





Continuity

HEATER AND AIR CONDITIONING 1-79

TROUBLESHOOTING
FAN CONTROL KNOB (FAN SWITCH)
Current flows to the blower motor through the Heater & A/C relay (X-11) to activate the rotation of the blower motor
by turning “ON” the fan control knob (fan switch). Blower motor speed is controlled in stages by the resistor, by
operating the switch from “LOW” to “HIGH.”

D08R300046-X2

1-80 HEATER AND AIR CONDITIONING

BLOWER MOTOR DOES NOT RUN


Replace
YES

Is No.SBF-8 (30A) slow blow fuse OK?

Is heater & A/C relay (X-11) OK?
YES

Is resistor OK?
YES

Is fan control knob (Fan switch) OK?
YES
YES

Check to see if battery voltage is present at
chassis side connector terminal No.C105-1 is there a
battery voltage?

Turn the ignition switch "ON" (Engine is running)

Fan control knob (Fan switch) "ON"

Is blower motor OK?
YES
Poor ground or open circuit either between chassis
side connector terminal No.C105-2 and No.C104-3
or No.B13-1 and body ground No.C-109.
NO
Replace
NO
Replace
NO
NO
Replace control lever
assembly
Replace
NO
NO
Open circuit between
No.SBF-8 (30A) slow blow
fuse and No.C105-1.

HEATER AND AIR CONDITIONING 1-81

BLOWER MOTOR DOES NOT RUN IN CERTAIN POSITION

A 1: (Low)
Blower motor does no
tB 2: (Medium Low) Position
run at
C 3: (Medium Hi)

D 4: (High)
* Checkin
g is performed only when in the malfunction
mode.


Is resist or OK?
YES


Is fan control knob (Fan switch) OK?
YES
Condition:


O
pen circuit between chassis side connector
terminal No. C104-2 and No. B13-3
B Condition :


O
pen circuit between chassis side connector
terminal No. C104-4 and No. B13-6
C Condition:


O
pen circuit between chassis side connector
terminal No. C104-1 and No. B13-5
D Condition:


O
pen circuit between chassis side connector
terminal No. C105-2 a nd No. B13-4
Replace
NO
NO
Replace control leverassembly A

1-82 HEATER AND AIR CONDITIONING

BLOWER MOTOR DOES NOT STOP AT “OFF” POSITION


Is fan control knob (Fan switch) OK?
YES
Short circuit between chassis side connector terminal

No.
C105-2 and No. C104-3
(or)


No. C105-2 and No. B13-4
(or)


No. C104-1 and No. B13-5
(or)


No. C104-4 and No. B13-6

(or)

No. C104-2 and No. B13-3
NO
Replace control lever assembly

HEATER AND AIR CONDITIONING 1-83

AIR CONDITIONING CYCLE TROUBLESHOOTING

TROUBLE POSSIBLE CAUSE CORRECTION
No cooling or
insufficient
cooling
1. Magnetic clutch does not run


Refer to “MAGNETIC CLUTCH”
troubleshooting in this section
2. Compressor is not rotating properly

Drive belt loosened or broken

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


Magnetic clutch face is not clean and
slips
Clean the magnetic clutch face or replace




Incorrect clearance between magnetic
drive plate and pulley

Adjust the clearance (Refer to
“COMPRESSOR OVERHAUL”



Compressor oil leaks from shaft seal or
shell

Replace the compressor




Compressor seized

Replace the compressor

3. Insufficient or excessive charge of
refrigerant

Discharge and recover refrigerant.
Recharge to specified amount.
4. Leaks in the refrigerant system




Check refrigerant system for leaks and
repair as necessary
Discharge and recover refrigerant.
Recharge to specified amount.
5. Condenser clogged or insufficient radiation


Clean the condenser or replace as
necessary


Check radiator or condenser fan function

6. Temperature control link unit of the heater
unit defective

Repair the link unit

7. Unsteady operation due to foreign
substance in expansion valve

Replace the expansion valve

8. Poor operation of electronic thermostat


Check electronic thermostat and replace
as necessary
Insufficient
velocity
of cooling air

1. Evaporator clogged or frosted


Check evaporator core and replace or
clean the core
2. Air leaking from cooling unit or air duct

Check evaporator and duct connection,
then repair as necessary

3. Blower motor does not rotate prop-erly


Refer to “FAN CONTROL KNOB (FAN
SWITCH)” troubleshooting in this section

* For the execution of the charging and discharging operation in the table above, refer to the “RECOVERY,
RECYCLING, EVACUATING AND CHARGING” in this section.

1-84 HEATER AND AIR CONDITIONING

f06r300014
CHECKING REFRIGERANT SYSTEM
WITH MANIFOLD GAUGE
Conditions;


Ambient temperature at approx. 30
35
C (86
95
F)


Run the engine at Idling

A/C switch is “ON”


Run the blower motor at “4” (high) position


Temperature control knob sets at “MAX COLD”


Air source selector lever at “CIRC”


Close the all doors
Normal pressures kPa (kg/cm
2 / PSI);
Low-pressure side:
Approx. 127 – 245 (1.3 – 2.5 / 18 – 36)
High-pressure side:
Approx. 1373 – 1670 (14 – 17 / 199 – 242)
Connect the manifold gauge
Low-pressure hose (LOW)  Suction side
High-pressure hose (HI)  Discharge side

HEATER AND AIR CONDITIONING 1-85

RESULT SYMPTOM TROUBLE CAUSE CORRECTION
Discharge
(High)
pressure
gauge
abnormally
high Reduced or no air flow through
the condenser


Condenser clogged or dirty


Radiator (condenser) fan
does not operate properly

Clean


Check cooling fan
operation
No bubbles in sight glass when
condenser is cooled by water
(Insufficient cooling)




Excessive refrigerant in
system





Check sight glass.
(See “Reading Sight
Glass”)


Discharge and
recover refrigerant.
Recharge to specified
amount
After stopping air conditioning,
pressure drops approx. 196 kPa
(2.0kg/cm
2 / 28 PSI) quickly

Air in system


Evacuate and charge
refrigerant system
Discharge
(High)
pressure
gauge
abnormally
low Insufficient cooling and excessive
bubbles in the sight glass







Insufficient refrigerant in
system







Check sight glass.
(See “Reading Sight
Glass”)

Check for leaks


Discharge and
recover refrigerant.
Recharge to specified
amount
Low pressure gauge indicates
vacuum

Clogged or defective
expansion valve

Replace the
expansion valve
Frost or dew on refrigerant line
before and after receiver/ drier or
expansion valve, and low pres-
sure gauge indicates vacuum
Restriction caused by debris
or moisture in receiver/drier


Check system for
restriction and
replace receiver/drier

After turning off air conditioning,
high and low pressure gauge
balanced quickly


Compressor seal defective


Poor compression due to
defective compressor
gasket

Replace or repair
compressor
Suction
(Low)
pressure
gauge
abnormally
high Low pressure gauge is lowered
after condenser is cooled by
water


Excessive refrigerant in
system



Discharge and
recover refrigerant
Recharge to specified
amount
Low pressure hose temperature
around the compressor refrigerant
line connector is lower than
around evaporator



Unsatisfactory valve
operation due to defective
temperature sensor of
expansion valve


Expansion valve opens too
long

Replace the
expansion valve




After turning off air conditioning,
high and low pressure gauge is
balanced quickly

Compressor gasket is
defective


Replace


Air conditioning turns off before
passenger compartment is
sufficiently
cool
Electronic thermostat
defective

Check the electronic
thermostat and
replace as necessary


* For the charging and discharging operations in the table above, refer to “RECOVERY, RECYCLING,
EVACUATION AND CHARGING” in this section.

1-86 HEATER AND AIR CONDITIONING

RESULT SYMPTOM TROUBLE CAUSE CORRECTION
Suction
(Low)
pres-sure
abnormally
low
Condenser is not hot and
excessive bubble in sight glass







Insufficient refrigerant








Check sight
glass.(See “Reading
Sight Glass”)


Check for leaks


Discharge and
recover refrigerant.
Recharge to specified
amount
Frost on the expansion valve inlet
line

Expansion valve clogged


Replace the
expansion valve

A distinct difference in
temperature between the inlet and
outlet refrigerant lines of the
receiver/drier

Receiver/drier clogged




Replace the receiver/
drier


Expansion valve outlet refrigerant
line is not cold and low-pressure
gauge indicates vacuum



The temperature sensor of
the expansion valve is
defective, and the valve
cannot regulate the correct
flow of the refrigerant

Replace the
expansion valve



Discharge temperature is low and
air flow from vents is restricted

Frozen evaporator core fins


Check electronic
thermostat and
replace as necessary
Low-pressure gauge reading is
low, or a vacuum reading may be
shown

Clogged or blocked
refrigerant line


Replace refrigerant
line
Suction
(Low) and
Discharge
(High)
pressure
abnor-
mally
high
No bubbles in sight glass after
condenser is cooled by water
(Insufficient cooling)





Excessive refrigerant in
system






Check sight
glass.(See “Reading
Sight Glass”)


Discharge and
recover refrigerant.
Recharge to specified
amount
Reduce air flow through con-
denser


Condenser clogged

Radiator (condenser) fan
does not rotate properly

Clean

Check cooling fan
operation
Suction (Low) pressure hose is
not cold

Air in system

Evacuate and charge
refrigerant
Suction
(Low) and
Discharge
(High)
pres-sure
abnor-
mally
low
Insufficient cooling and excessive
bubbles in the sight glass

Insufficient refrigerant in
system


Check sight glass.
(See “Reading Sight
Glass”)


Check for leaks

Discharge and
recover refrigerant.
Recharge to specified
amount

HEATER AND AIR CONDITIONING 1-87

MAGNETIC CLUTCH
When the A/C switch and the fan control knob (fan switch) are turned on with the engine running, current flows
through the thermostat and the compressor relay to activate the magnetic clutch.
The air conditioning can be stopped by turning off the A/C 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 ECM
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.