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Downloaded from www.Manualslib.com manuals search engine 1B-4 AIR CONDITIONING (OPTIONAL)
Refrigerant Circulation
Refrigerant Type
Whether the A/C in the vehicle being serviced uses HFC-134a
(R-134a) or CFC-12 (R-12) is indicated on compressor label (1).
Also, it can be checked by the shape of the service (charge) valve
(2).
A: Liquid 1. Compressor 4. Receiver / dryer 7. Evaporator
B: Vapor 2. Magnet clutch 5. Dual pressure switch
C: Superheated vapor 3. Condenser assembly 6. Expansion valve
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Diagnosis
General Diagnosis Table
Condition Possible Cause Correction
Cool air won’t come
out (A/C system won’t
operative)No refrigerant Perform recover, evacuation and charging.
Fuse blown Check fuses in main and circuit fuse
boxes, and check short circuit to ground.
A/C switch faulty Check A/C switch.
Blower fan switch faulty Check blower fan switch referring to Sec-
tion 1A.
A/C evaporator thermistor faulty Check A/C evaporator thermistor.
Dual pressure switch faulty Check dual pressure switch.
Wiring or grounding faulty Repair as necessary.
ECT sensor faulty Check ECT sensor referring to Section 6E.
ECM and its circuit faulty Check ECM and its circuit referring to Sec-
tion 6E.
4WD controller faulty Check 4WD controller referring to Section
3D.
Cool air won’t come
out (A/C compressor
won't operative)ECM faulty Check ECM and its circuit referring to Sec-
tion 6E.
Magnet clutch faulty Check magnet clutch.
Compressor drive belt loosen or broken Adjust or replace drive belt.
Compressor faulty Check compressor.
Cool air won’t come
out (A/C condenser
cooling fan motor
won’t operative)Fuse blown Check “A/C” fuse in main fuse box, and
check short circuit to ground.
Wiring or grounding faulty Repair as necessary.
Condenser cooling fan motor relay
faultyCheck condenser cooling fan motor relay.
Condenser cooling fan motor faulty Check condenser cooling fan motor.
Cool air won’t come
out (Blower fan motor
won’t operative)Fuse blown Check fuses in main and circuit fuse
boxes, and check short circuit to ground.
Blower fan motor resistor faulty Check blower fan motor resistor referring
to Section 1A.
Blower fan switch faulty Check blower fan switch referring to Sec-
tion 1A.
Wiring or grounding faulty Repair as necessary.
Blower fan motor faulty Check blower fan motor referring to Sec-
tion 1A.
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Cool air won’t come
out or insufficient
cooling (A/C system
normal operative)Insufficient or excessive charge of
refrigerantCheck charge of refrigerant and system for
leaks.
Condenser clogged Check condenser.
A/C evaporator clogged or frosted Check A/C evaporator and A/C evaporator
thermistor.
A/C evaporator thermistor faulty Check A/C evaporator thermistor.
Expansion valve faulty Check expansion valve.
Receiver / dryer clogged Check receiver / dryer.
Compressor drive belt loosen or broken Adjust or replace drive belt.
Magnetic clutch faulty Check magnetic clutch.
Compressor faulty Check compressor.
Air in A/C system Replace receiver / dryer, and perform
evacuation and charging.
Air leaking from cooling unit or air duct Repair as necessary.
Heater and ventilation system faulty Check air inlet box (cooling unit), heater
control lever assembly and heater unit
referring to Section 1A.
Blower fan motor faulty Check blower fan motor referring to Sec-
tion 1A.
Excessive compressor oil existing in
A/C systemPull out compressor oil in A/C system cir-
cuit, and replace compressor.
Cool air won’t come
out only intermittentlyWiring connection faulty Repair as necessary.
Expansion valve faulty Check expansion valve.
Excessive moisture in A/C system Replace receiver / dryer, and perform
evacuation and charging.
Magnetic clutch faulty Check magnetic clutch.
Excessive charge of refrigerant Check charge of refrigerant.
Thermal switch faulty Check thermal switch.
Cool air comes out
only at high speedCondenser clogged Check A/C condenser.
Insufficient charge of refrigerant Check charge of refrigerant.
Air in A/C system Replace receiver / dryer, and perform
evacuation and charging.
Compressor drive belt loosen or broken Adjust or replace drive belt.
Compressor faulty Check compressor.
Cool air won’t come
out only at high speedExcessive charge of refrigerant Check charge refrigerant.
A/C evaporator frosted Check A/C evaporator and A/C evaporator
thermistor.
Insufficient velocity of
cooled airA/C evaporator clogged or frosted Check A/C evaporator and A/C evaporator
thermistor.
Air leaking from cooling unit or air duct Repair as necessary.
Blower fan motor faulty Check blower fan motor referring to Sec-
tion 1A.
Wiring or grounding faulty Repair as necessary. Condition Possible Cause Correction
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Abnormal Noise Diagnosis
There are various types of noise, ranging from those produced in the engine compartment to those from the
passenger compartment, also from rumbling noises to whistling noises.
Abnormal noise from compressor
Abnormal noise from magnetic clutch
Abnormal noise from tubing
Abnormal noise from condenser
Condition Possible Cause Correction
During compressor
operation, a rumbling
noise is heard propor-
tional to engine revo-
lutions.Inadequate clearance in piston area (piston or
swash-plate).Repair or replace compressor as
necessary
A loud noise is heard
at a certain rpm, dis-
proportionately to
engine revolution.Loose or faulty compressor drive belt. Adjust drive belt tension, or replace
belt.
Loose compressor mounting bolts. Retighten mounting bolts.
A loud rattle is heard
at low engine rpm.Loose compressor clutch plate bolt. Retighten clutch plate bolt.
Replace compressor if it was oper-
ated in this condition for a long
time.
Condition Possible Cause Correction
A rumbling noise is
heard when compres-
sor is not operating.Worn or damaged bearings. Replace magnet clutch assembly.
A chattering noise is
heard when compres-
sor is engaged.Faulty clutch clearance (excessive). Adjust clutch clearance.
Worn clutch friction surface. Replace magnet clutch assembly.
Compressor oil leaked from lip type seal. Replace lip type seal.
Contaminating the friction surface. Replace compressor body assem-
bly.
Condition Possible Cause Correction
A droning noise is
heard inside vehicle,
but not particularly
noticeable in engine
compartment.Faulty tubing clamps. Reposition clamps or increase the
number of clamps.
Resonance caused by pulsation from variations
in refrigerant pressure.Attach a silencer to tubing, or mod-
ify its position and length.
Condition Possible Cause Correction
Considerable vibra-
tion in condenser.Resonance from condenser bracket and body. Firmly insert a silencer between
condenser bracket and body.
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Abnormal noise from crankshaft pulley
Abnormal noise from tension pulley
Abnormal noise from A/C evaporator
Abnormal noise from blower fan motor
Condition Possible Cause Correction
A large rattling noise
is heard at idle or sud-
den acceleration.Loosen crankshaft pulley bolt. Retighten bolt.
Condition Possible Cause Correction
Clattering noise is
heard from pulley.Worn or damaged bearing. Replace tension pulley.
Pulley cranks upon
contact.Cracked or loose bracket. Replace or retighten bracket.
Condition Possible Cause Correction
Whistling sound is
heard from A/C evapo-
rator.Depending on the combination of the interior /
exterior temperatures, engine rpm and refriger-
ant pressure, the refrigerant flowing out of the
expansion valve may, under certain conditions,
make a whistling sound.At times, slightly decreasing refrig-
erant volume may stop this noise.
Inspect expansion valve and
replace if faulty.
Condition Possible Cause Correction
Blower fan motor
emits a chirping
sound in proportion to
its speed of rotation.Worn or damaged motor brushes or commuta-
tor.Repair or replace blower fan motor.
Fluttering noise or
large droning noise is
heard from blower fan
motor.Leaves or other debris introduced from fresh air
inlet to blower fan motor.Remove debris and make sure that
the screen at fresh air inlet is intact.
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Quick Checking of Refrigerant Charge
The following procedure can be used for quickly checking whether
the A/C system has a proper charge of refrigerant or not.
Run engine at fast idle, and operate A/C at its maximum cooling
capacity for a few minutes. Then, look at the sight glass (1) on
receiver / dryer (2) and compare what is observed with the symp-
toms listed in below.
CHECKING REFRIGERANT CHARGE
3. Bubbles
Symptom Charge of refrigerant condition Correction
Bubbles observed in sight glass Insufficient charge of refrigerant in
systemCheck system for leaks with a
leak tester.
No bubbles observed in sight glass No or insufficient charge of refrig-
erant in systemRefer to the items 3 and 4.
No temperature difference between
compressor inlet and outletEmpty or nearly empty system Evacuate and charge system and
then check it for leaks with a leak
tester.
Noticeable temperature difference
between compressor inlet and outletProper or too much charge of
refrigerant in systemRefer to the items 5 and 6.
When A/C is turned OFF, refrigerant in
sight glass clears immediately and
remains clearToo much charge of refrigerant in
systemDischarge excess refrigerant in
order to obtain a specified charge.
When A/C is turned OFF, refrigerant in
sight glass once produces bubbles and
then clearsProper charge of refrigerant in
systemNo correction needed because
charge of refrigerant is normal.
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Downloaded from www.Manualslib.com manuals search engine 1B-10 AIR CONDITIONING (OPTIONAL)
Performance Diagnosis
1) Confirm that vehicle and environmental conditions are as fol-
lows.
Vehicle is not exposed to direct sun.
Ambient temperature is within 15 – 35 °C (59 – 95 °F).
2) Make sure that high pressure valve (1) and low pressure
valve (2) of manifold gauge set (3) are firmly closed.
3) Connect high pressure charging hose (4) to high pressure
service valve (5), and connect low pressure charging hose
(6) to low pressure service valve (7).
4) Bleed the air in charging hoses (4), (6) by loosening their
respective nuts on manifold gauge set (3), utilizing the refrig-
erant pressure. When a hissing sound is heard, immediately
tighten nut.
5) Warm up engine to normal operating temperature (engine
coolant temperature at 80 – 90 °C (176 – 194 °F)) and keep
it at specified idle speed. (Radiator cooling fan should not be
working when checking pressure and temperature.)
6) Turn A/C switch ON, and set blower switch at “HI” (3rd posi-
tion), temperature knob at “COOL” air outlet control knob at
“FACE” and fresh / circulation control knob at “CIRCULA-
TION”. (Confirm that A/C compressor and radiator / con-
denser cooling fan are working.)
Keep all windows, doors and engine food open.
Performance diagnosis condition
7) With dry bulb thermometer (1) inserted into center duct air
outlet and another one set near evaporator air inlet, read
temperature indicated on each thermometer. CAUTION:
Do not interchange high and low pressure charging
hoses by mistake.
Ambient temperature 15 – 35 °C (59 – 95 °F)
Engine rpm Keep to 1,500 rpm.
Blower fan motor switch “H” (3rd position)
Temperature control “Cool”
Air outlet control “Face”
Vehicle doors All open
Air inlet door position Recirculation
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8) Check if each pressure on low side and on high side is within
shaded range of the graph.
If each gauge reading is out of specified pressure, correct
defective part referring to “Performance Diagnosis Table” in
this section.
Low side and high side pressure example :
9) Check inlet port temperature-to-outlet port temperature rela-
tionship using graph.
For example, if evaporator inlet port temperature is 25 °C
(77 °F) and center duct air outlet temperature is 8 °C
(46.4 °F), their crossing point is within acceptable range as
shown in the graph.
If crossing point is out of acceptable range, diagnose trouble
referring to “Performance Diagnosis Table” in this section. NOTE:
Pressure registered on gauge varies with ambient tem-
perature. Therefore, use graph when determining if pres-
sures are normal or not.
Gauges should read as follows when ambient tempera-
ture is 30 °C (86 °F).
Pressure on high pres-
sure gauge1400 – 1750 kPa
14.0 – 17.5 kg/cm
2
199.1 – 248.9 psi
Pressure on low pressure
gauge230 – 350 kPa
2.3 – 3.5 kg/cm
2
32.7 – 49.8 psi