1B-12 AIR CONDITIONING (OPTIONAL)
PERFORMANCE DIAGNOSIS TABLE
HIGH PRESSURE GAUGE
LOW PRESSURE GAUGE
THERMOMETER AT CENTER DUCT
NOTE:
If ambient temperature is approximately 30°C (86°F), it is possible to diagnose A/C system in detail
referring to “DETAIL DIAGNOSIS TABLE (AMBIENT TEMPERATURE AT 30 °C (86°F))” under “PER-
FORMANCE DIAGNOSIS” in this section.
Condition Possible Cause Correction
Pressure high
(“A” area of high side
graph)Refrigerant overcharged Recharge.
Expansion valve frozen or clogged Check expansion valve.
Clogged refrigerant passage of high side Clean or replace.
Radiator/condenser cooling fan malfunction (Insufficient
cooling of condenser)Check radiator/condenser cooling fan.
Dirty or bent condenser fins (Insufficient cooling of con-
denser)Clean or repair.
Compressor malfunction (Insufficient oil etc.) Check compressor.
Engine overheat Check engine cooling system referring to
Section 6B.
Pressure low
(“B” area of high side
graph)Insufficient refrigerant (Insufficient charge or leakage) Check for leakage, repair if necessary
and recharge.
Expansion valve malfunction (valve opens too wide) Check expansion valve.
Compressor malfunction (Insufficient compression) Check compressor.
Condition Possible Cause Correction
Pressure high
(“C” area of low side
graph)Expansion valve malfunction (valve opens too wide) Check expansion valve.
Compressor malfunction (Insufficient compression) Check compressor.
Pressure low
(“D” area of low side
graph)Insufficient refrigerant (Insufficient charge or leakage) Check for leakage, repair if necessary
and recharge.
Expansion valve malfunction (valve opens too narrow) Check expansion valve.
Clogged refrigerant passage (crashed pipe) Repair or replace.
Condition Possible Cause Correction
Outlet air temperature at
center duct is high
(Crossing point is in area
“E”)Insufficient or excessive charge of refrigerant Check refrigerant pressure.
Dirty or bent A/C evaporator fins Clean or repair.
Air leakage from cooling (heater) unit or air duct Repair or replace.
Malfunctioning, switch over function of door in cooling
(heater) unitRepair or replace.
Compressor malfunction Check compressor.
Outlet air temperature at
center duct is low
(Crossing point is in area
“F”)Insufficient air volume from center duct (Heater blower
malfunction)Check blower motor and fan.
Compressor malfunction Check compressor.
AIR CONDITIONING (OPTIONAL) 1B-13
DETAIL DIAGNOSIS TABLE (AMBIENT TEMPERATURE AT 30°C (86°F))
Condition
Possible Cause Correction MANIFOLD
GAUGEMPa
(kg/cm
2)
(psi)Detail
Lo Hi
0.23 – 0.35
(2.3 – 3.5)
(33 – 50)1.4 – 1.75
(14 – 17.5)
(200 – 249)Normal condition––
Negative
pressure0.5 – 0.6
(5 – 6)
(71.2 – 85.3)The low pressure side
reads a negative pressure,
and the high pressure side
reads an extremely low
pressure.
Presence of frost around
tubing to and from receiver/
dryer and expansion valve.Dust particles or water drop-
lets are either stuck or frozen
inside expansion valve, pre-
venting the refrigerant from
flowingClean expansion valve.
Replace it if it cannot be
cleaned.
Replace receiver/dryer.
Evacuate the A/C system and
recharge with fresh refriger-
ant.
Normal :
0.23 – 0.35
(2.3 – 3.5)
(33 – 50)
↑ ↓
↑ ↓↑ ↓ ↑ ↓
Abnormal :
Negative
pressureNormal :
1.4 – 1.75
(14 – 17.5)
(200 – 249)
↑ ↓
↑ ↓↑ ↓ ↑ ↓
Abnormal :
0.7 – 1.0
(7 – 10)
(100 – 142)During A/C operation, the
low pressure side some-
times indicates negative
pressure, and sometimes
normal pressure. Also high
pressure side reading fluc-
tuates between the abnor-
mal and normal pressure.Expansion valve is frozen due
to moisture in the system, and
temporarily shuts off the
refrigeration cycleReplace expansion valve.
Replace receiver/dryer.
Evacuate A/C system and
recharge with fresh refriger-
ant.
0.05 – 0.15
(0.5 – 1.5)
(4.2 – 21.3)0.7 – 1.0
(7 – 10)
(100 – 142)Both low and high pressure
sides indicate low readings.
Continuous air bubbles are
visible through sight glass.
Output air is slightly cold.Insufficient refrigerant in sys-
tem
(Refrigerant leaking)Using leak detector, check for
leaks and repair as neces-
sary.
Recharge refrigerant to a
specified amount.
If the pressure reading is
almost 0 when the manifold
gauges are attached, check
for any leaks, repair them,
and evacuate the system.
0.4 – 0.6
(4 – 6)
(56.9 – 85.3)Pressure on low pressure
side is high.
Pressure on high pressure
side is low.
Both pressure becoming
equal right after A/C is
turned OFF.Internal leak in compressor Inspect compressor and
repair or replace as neces-
sary.
1B-14 AIR CONDITIONING (OPTIONAL)
0.35 – 0.45
(3.5 – 4.5)
(50 – 64)2.0 – 2.5
(20 – 25)
(285 – 355)High pressure reading on
both low and high pressure
sides.
Air bubbles are not visible
even when engine rpm is
lowered.Overcharged A/C system Adjust refrigerant to specified
amount.
Faulty condenser cooling
operationClean condenser.
Faulty radiator/condenser
cooling fan operationInspect and repair radiator/
condenser cooling fan.
High pressure reading on
both low and high pressure
sides.
Low pressure side tubing is
not cold when touched.
Air bubbles are visible
through sight glass.Presence of air in A/C system
(Improperly evacuated)Replace receiver/dryer.
Inspect quantity of compres-
sor oil and presence of con-
taminants in oil.
Evacuate system and
recharge with fresh refriger-
ant.
0.45 – 0.55
(4.5 – 5.5)
(64 – 78)High pressure reading on
both low and high pressure
sides.
Large amount of frost or
dew on the low pressure
side tubing.Faulty expansion valve
Refrigerant flow is not regu-
lated properlyReplace expansion valve. Condition
Possible Cause Correction MANIFOLD
GAUGEMPa
(kg/cm
2)
(psi)Detail
Lo Hi
AIR CONDITIONING (OPTIONAL) 1B-15
COMPRESSOR DRIVE BELT
INSPECTION
Check compressor drive belt (6) for wear and cracks, and
replace as required.
Check compressor drive belt (6) tension by measuring how
much it deflects when pushed at intermediate point between
compressor pulley (1) and tension pulley (2) with about 100
N (10 kg) force after crankshaft pulley 1 rotating.
If belt tension is without specification, adjust belt tension
referring to below procedures.
Compressor drive belt tension
“a” : 3 – 5 mm (0.12 – 0.20 in.)
New compressor drive belt tension
“a” : 2 – 4 mm (0.08 – 0.16 in.)
ADJUSTMENT
1) Loosen tension pulley nut (3).
2) Adjust belt tension by tighten or loosen tension pulley adjust-
ing bolt (4).
3) Tighten tension pulley nut (3).
4) Turn the crank pulley (5) 1 revolution, then check belt ten-
sion.
REPLACEMENT
1) Loosen tension pulley nut (3).
2) Loosen belt tension by loosen tension pulley adjusting bolt
(4).
3) Remove compressor drive belt (6).
4) Install new compressor drive belt.
5) Adjust belt tension referring to above procedure.
1B-16 AIR CONDITIONING (OPTIONAL)
ELECTRICAL DIAGNOSIS
WIRING DIAGRAM
1. Blower fan motor 6. Radiator/condenser cooling fan relay No.2 11. Ignition switch 16. Main fuse box
2. Blower fan motor resistor 7. Radiator/condenser cooling fan relay No.3 12. A/C evaporator temperature sensor 17. Generator
3. Blower fan switch and A/C switch 8. Radiator/condenser cooling fan motor 13. ECT sensor 18. Compressor
4. A/C refrigerant pressure switch 9. Compressor thermal switch 14. Lighting switch
5. Radiator/condenser cooling fan relay No.1 10. Main relay 15. Circuit fuse box
AIR CONDITIONING (OPTIONAL) 1B-17
A/C SYSTEM INSPECTION OF ECM AND ITS
CIRCUITS
ECM and its circuits can be checked at ECM wiring couplers by
measuring voltage.
VOLTAGE CHECK
1) Remove ECM from vehicle by referring to “ECM (PCM)
REMOVAL AND INSTALLATION” in Section 6E1.
2) Connect ECM couplers (1) to ECM (2).
3) Check voltage at each terminal of couplers connected.CAUTION:
ECM cannot be checked by itself. It is strictly prohibited
to connect voltmeter or ohmmeter to ECM with couplers
disconnected from it.
NOTE:
As each terminal voltage is affected by the battery volt-
age, confirm that it is 11 V or more when ignition switch
is ON position.
[A] : Fig. A
[B] : Fig. B
1B-18 AIR CONDITIONING (OPTIONAL)
System Circuit
Terminal arrangement of ECM coupler (Viewed from harness side)
1. Blower fan motor 8. Main relay A. To “HTR” fuse (25 A) in circuit fuse box
2. Blower fan switch 9. Radiator/condenser cooling fan motor relay No.1 B. To main fuse (15 A)
3. A/C switch 10. Radiator/condenser cooling fan motor relay No.2 C. To main fuse (30 A)
4. A/C refrigerant pressure switch 11. Radiator/condenser cooling fan motor relay No.3
5. Compressor 12. Radiator/condenser cooling fan motor
6. A/C evaporator temperature sensor 13. Engine earth
7. ECT sensor 14. ECM
AIR CONDITIONING (OPTIONAL) 1B-19
ECM Voltage Values Table for Relation of A/C Control
Terminal Wire Circuit Measurement
groundNormal value Condition
C41-1 PNK/BLK Compressor magnet
clutch outputGround to engine
(Fig B)12 – 15 V Except the above-mentioned condition with engine
running
0 – 1 V Blower fan switch and A/C switch ON with engine
running
C41-5 BLK/RED Main power supply for
ECMGround to engine
(Fig B)10 – 14 V Ignition switch ON with engine stopped
C41-6 BLK/RED Main power supply for
ECMGround to engine
(Fig B)10 – 14 V Ignition switch ON with engine stopped
C41-10 BRN/
WHTMain relay drive Ground to engine
(Fig B)0.5 – 1.2 V Ignition switch ON with engine stopped
10 – 14 V Ignition switch OFF
C41-16 YEL/GRN A/C switch input Ground to engine
(Fig B)12 – 15 V Blower fan switch or A/C switch OFF with engine
running
0 – 1 V Blower fan switch and A/C switch ON with engine
running
C41-18 BLU Radiator/condenser
cooling fan relay out-
put 1Ground to engine
(Fig B)0 – 1 V Blower fan switch and A/C switch ON
Engine coolant temperature at more than 97.5°C
(207.5°F) with engine running
12 – 15 V Blower fan motor switch or A/C switch OFF
Engine coolant temperature at less than 97.5°C
(207.5°F) with engine running
C42-1 BLK/ORN Main ground for ECM Ground to body
(Fig A)–0.5 – 1 V Engine running
C42-2 BLK ECM ground for
power circuitGround to body
(Fig A)–0.5 – 1 V Engine running
C42-3 BLK/ORN ECM ground for
power circuitGround to body
(Fig A)–0.5 – 1 V Engine running
C42-10 ORN Sensor ground for
ECT sensorGround to body
(Fig A)–0.5 – 1 V Engine running
C42-14 LT GRN/
BLKECT sensor input Ground to engine
(Fig B)0.71 – 0.75 V
(298 – 320 Ω
)Engine coolant temperature at approximately 80°C
(176°F) with engine running
0.35 – 0.37 V
(135 – 144 Ω
)Engine coolant temperature at Approximately
110°C (230°F) with engine running
If the temperature is more than 114°C (232°F),
compressor and condenser cooling fan should be
stop (come back at less than 112°C (230°F))
C42-18 PNK/GRN Medium pressure
switch inputGround to engine
(Fig B)–0.5 – 1 V Medium pressure switch of A/C refrigerant pres-
sure switch ON
12 – 15 V Medium pressure switch of A/C refrigerant pres-
sure switch OFF
G02-3 PPL/YEL Radiator/Condenser
cooling fan relay out-
put 2Ground to engine
(Fig B)0 – 1 V Blower fan motor switch ON, A/C switch ON and
medium pressure switch OFF
Engine coolant temperature at more than 102.5°C
(216.5°F) with engine running
12 – 15 V Blower fan motor switch OFF, A/C switch OFF or
medium pressure switch ON
Engine coolant temperature at less than 102.5°C
(216.5°F) with engine running
G02-10 ORN Sensor ground for A/C
evaporator tempera-
ture sensorGround to engine
(Fig A)–0.5 – 1 V Engine running
G02-13 PNK/BLU Blower fan speed
inputGround to engine
(Fig B)0 – 1 V Blower fan motor switch “ML”, “MH”, or “H” with
engine running
4 – 7 V Blower fan motor switch “L” position with engine
running
12 – 15 V Blower fan motor switch OFF with engine running
G02-14 WHT/BLK A/C evaporator tem-
perature sensor inputGround to engine
(Fig B)2.09 – 2.17 V
(1940 – 2060 Ω
)A/C evaporator temperature at approximately 25°C
(77°F) with engine running
3.52 – 3.59 V
(6450 – 6850 Ω
)A/C evaporator temperature at approximately 0°C
(32°F) with engine running
If the temperature is less than approximately 2.5°C
(36.5°F), compressor and condenser cooling fan
should be stop (come back at more than approxi-
mately 4°C (39.2°F)