Page 839 of 1500

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-138
16 Potentiometer power supply Ignition switch: ON 5 V
17 Power transistor (BASE) When the blower speed
selection dial shows Maximum
air volume.1 V
18 Power transistor
(COLLECTOR)When the blower speed
selection dial shows Maximum
air volume.12.1 V
19 Photo sensor Ignition switch: ON 5 V
20 Sensors and potentiometers
groundAlways 0 V
21 Mode selection damper control
motor potentiometer inputWhen the damper is moved to
the FACE position. 4 V
22 Interior temperature sensor Ignition switch: ON 5 V
23 Ambient temperature sensor
inputWhen sensor temperature is
25
C (77F) [4 k]1.9 V
24 Air thermo sensor input When sensor temperature is
25
C (77F) [1.5 k]2.2 V
25 Photo sensor ground Ignition switch: ON 0 V
26 A/C pressure sensor at 2.6 MPa 3.9 V
27 Ground Always 0 V
28 Power supply to the ignition
switch (IG2)Ignition switch: ON Battery positive voltage
29 Air mixing damper control motor
potentiometer inputWhen the damper door is
moved to the MAX. HOT
position.1.4 V
30 Illumination ground Always 0 V
31 ILL power supply Lighting switch: ON Battery positive voltage
34 A/C pressure sensor ground Always 0 V
36 Power supply to the ignition
switch (ACC)Ignition switch: ON Battery positive voltage TERMINAL
NO.CHECK ITEM CHECKING REQUIREMENTS NORMAL CONDITION
Page 842 of 1500

ON-VEHICLE SERVICE
HEATER, AIR CONDITIONING AND VENTILATION55-141
ON-VEHICLE SERVICE
REFRIGERANT LEVEL TESTM1552008400408
Use the refrigerant recovery station to remove all of the refrig-
erant, and then calculate the amount of the refrigerant and
charge it.
A/C COMPRESSOR CLUTCH TESTM1552019900032
1. Disconnect the air conditioning compressor clutch connector
to the air conditioning compressor clutch.
2. Connect positive battery voltage directly to the connector for
the air conditioning compressor clutch.
3. If the air conditioning compressor clutch is normal, there will
be a "click." If the pulley and armature do not make contact
("no click"), there is a malfunction.
SIMPLE INSPECTION OF THE A/C PRESSURE
SENSOR
M1552014700118
1. Assemble a gauge manifold on the high pressure service
valve.
2. Disconnect the A/C pressure sensor connector and connect
special tool test harness MB991658 as shown in the illustra-
tion.
3. Turn ON the engine and then turn ON the air conditioner
switch.
Page 849 of 1500

ON-VEHICLE SERVICE
HEATER, AIR CONDITIONING AND VENTILATION55-148
POWER RELAY CHECKM1552008800321
BLOWER RELAY CONTINUITY CHECK
Hissing or swishing
noiseLow refrigerant quantity Refrigerant level Check system for leaks
and charge to
specification
Rattling (Internal
compressor)Lack of lubricating oil. In a
system with a gas leak
the oil has escaped with
the refrigerantRattling noise from
internal compressorRepalce the compressor
and also fix the system
leak to prevent
reoccurrance
Wooing (Resonant
noise)Drive accessory (P/S
pump, Alternator,etc)
resonating at specific
engine speedThe drive accessories for
vibrationStop vibrations of the
assembly or modify
transmission route to the
vehicle body
Cooing (Discharge
pulsation noise)Pressure fluctuation of
refrigerant discharged
from compressor, which
vibrates the high pressure
pipingRemove the piping
mounting clamps and
re-check. Hold the
condenser without
mountings by hand and
re-checkPut rubber bush between
pipe clamps and the
vehicle body. decrease
refrigerant to minimum
specified level. NOISE DESCRIPTION POSSIBLE CAUSE CHECK REPAIR
BATTERY
VOLTAGETESTER
CONNECTIONSPECIFIED
CONDITION
Not applied 4
5 Open circuit
Connect
terminal 1 to the
positive battery
terminal
Connect
terminal 3 to the
negative battery
terminal4
5 Less than 2 ohms
Page 850 of 1500

ON-VEHICLE SERVICE
HEATER, AIR CONDITIONING AND VENTILATION55-149
A/C COMPRESSOR CLUTCH RELAY CONTINUITY
CHECK
IDLE-UP OPERATION CHECK
M1552001600401
Before inspection and adjustment, set vehicle in the following
condition:
Engine coolant temperature: 80 90 C (176.0 194.0 F)
Lights, electric cooling fan and accessories: OFF
Transmission: Neutral ("N" or "P" position)
Steering wheel: Straightforward
1. Check whether or not the idle speed is the standard value.
Standard value: 680
50 r/min
2. Turn on the air conditioning switch and the blower speed
selection dial. Engine idling speed should be within the
standard value:
Standard value: 680
50 r/min
NOTE: The Electronic control unit determines whether the
A/C load is low or high according to the output signal from
the A/C-ECU.
NOTE: It is not necessary to make an adjustment, because
the idling speed is automatically controlled by the ENGINE
ECU. BATTERY
V O LTA G ETESTER
CONNECTIONSPECIFIED
CONDITION
Not applied 1
4 Open circuit
Connect
terminal 2 to the
positive battery
terminal
Connect
terminal 3 to the
negative battery
terminal1
4 Less than 2 ohms
Page 852 of 1500

HEATER UNIT, HEATER CORE, BLOWER ASSEMBLY AND EVAPORATOR UNIT
HEATER, AIR CONDITIONING AND VENTILATION55-151
HEATER UNIT, HEATER CORE, BLOWER ASSEMBLY AND
EVAPORATOR UNIT
REMOVAL AND INSTALLATIONM1552021400012
Before removing the front seat assembly, refer to GROUP 52B, Service Precautions
P.52B-16 and Air Bag Module and Clock Spring P.52B-237.
Pre-removal and Post-installation Operation
Refrigerant draining and Refilling (Refer to Charging and
Discharging P.55-142).
Engine coolant Draining and Refilling (Refer to GROUP
00, Engine coolant P.00-47).
Instrument Panel Removal and Installation (Refer to
GROUP 52A, Instrument Panel P.52A-4).
Steering Column Shaft Assembly Removal and Installa-
tion (Refer to GROUP 37A, Steering ShaftP.37-25).
Floor Console Removal and Installation (Refer to GROUP
52A, Floor Console P.52A-10).
Front Seat Assembly Removal and Installation (Refer to
GROUP 52A, Front Seat P.52A-21).
² Strut Tower Bar (Refer to GROUP 42, Removal And
InstallationP.42-12.)
REMOVAL STEPS
BATTERY
AIR CLEANER BODY (REFER TO
GROUP 15, AIR CLEANER
P.15-4.)
1. HEATER HOSE CONNECTION
<>2. SUCTION PIPE CONNECTION
<>3. LIQUID PIPE CONNECTION
4. O-RING
REAR HEATER DUCT A AND B
(REFER TO P.55-175.)
5. JUNCTION BLOCKREMOVAL STEPS (Continued)
Page 856 of 1500

HEATER UNIT, HEATER CORE, BLOWER ASSEMBLY AND EVAPORATOR UNIT
HEATER, AIR CONDITIONING AND VENTILATION55-155
INSPECTIONM1552014301157.
AIR MIXING DAMPER CONTROL MOTOR CHECK
Do not apply battery voltage when the damper is in the
MAX COOL or MAX HOT position.
Check the air mix damper control motor by the following proce-
dures.
.
POTENTIOMETER CHECK
While checking the air mix damper control motor, measure the
resistances between terminals numbers 3 and 5 and between
numbers 3 and 7. At this time, the resistances should change
gradually within the standard value.
Standard value: 1.7 (MAX HOT)
5.0 (MAX COOL) k
AIR THERMO SENSOR INSPECTION
.Measure the resistance between connector terminals 1 and 2
under at least two different temperatures. The resistance val-
ues should generally match those in the graph.
NOTE: The temperature at the check should not exceed the
range in the graph. LEVER POSITION BATTERY
CONNECTIONLEVER
OPERATION
At the MAX COOL
position
Connect
terminal 2 to the
positive battery
terminal
Connect
terminal 1 to the
negative battery
terminalThe lever moves
from the MAX
COOL position to
the MAX HOT
position
At the MAX HOT
position
Connect
terminal 1 to the
positive battery
terminal
Connect
terminal 2 to the
negative battery
terminalThe lever moves
from the MAX HOT
position to the MAX
COOL position
Page 859 of 1500

MOTORS AND TRANSISTOR
HEATER, AIR CONDITIONING AND VENTILATION55-158
INSPECTIONM1551006300338.
MODE SELECTION DAMPER CONTROL MOTOR
CHECK
Do not apply battery voltage when the damper is in the
FACE or DEF position.
Check the mode selection damper control motor by the follow-
ing procedures.
.
POTENTIOMETER CHECK
While checking the mode selection damper control motor, mea-
sure the resistances between terminal numbers 3 and 5 and
between terminal numbers 3 and 7. At this time, the resis-
tances should change gradually within the standard value.
Standard value: 0.8 (DEF)
4.8 (FACE) k
.
OUTSIDE/INSIDE AIR SELECTION DAMPER
CONTROL MOTOR CHECK
Cut off the battery voltage when the damper is in the
inside/outside air position.
Check the outside/inside air selection damper control motor by
the following procedures.LEVER POSITION BATTERY
CONNECTIONLEVER
OPERATION
At the FACE
position
Connect
terminal 2 to the
positive battery
terminal
Connect
terminal 1 to the
negative battery
terminalThe lever moves
from the FACE
position to the DEF
position
At the DEF position
Connect
terminal 1 to the
positive battery
terminal
Connect
terminal 2 to the
negative battery
terminalThe lever moves
from the DEF
position to the
FACE position
Page 860 of 1500
MOTORS AND TRANSISTOR
HEATER, AIR CONDITIONING AND VENTILATION55-159
.
BLOWER FAN AND MOTOR CHECK
When battery voltage is applied between the terminals, check
that the motor operates. Also, check that there is no abnormal
noise.LEVER POSITION BATTERY
CONNECTIONLEVER
OPERATION
At the inside
position
Connect
terminal 1 to the
positive battery
terminal
Connect
terminal 7 to the
negative battery
terminalThe lever moves
from the outside
position to the
inside position
At the outside
position
Connect
terminal 1 to the
positive battery
terminal
Connect
terminal 5 to the
negative battery
terminalThe lever moves
from the inside
position to the
outside position