1991 LEXUS SC400 light

INDICATOR
1. Turn the ignition switch on while pressing the ari conditioner control
switch and REC swich
simultaneously.
2. Check that all the indicators light up and go off at 1 second intervals 4 times in succession.
3. Check that the buzzer sounds when the indicators light up in 2.
HINT:
wAfter the indicator check is ended, the diagnostic code
check begins automatically.
w Press the OFF switch when desiring to cancel the check
mode.
DIAGNOSTIC CODE CHECK (SENSOR
CHECK)
1. Perform an indicator check. After the indicator check is completed, the system enters the diagnostic code check
mode automatically.
2. Read the code displayed on the panel. Refer to the list of
codes on page AC±28 when reading the codes. (Codes are
output at the temperature display.)
If the slower display ped is desired, press the FRS
switch and change it to stepped operation. Each time the
FRS
switch is pressed, the display changes by 1 step.
HINT:
w If the buzzer sounds when a code is being read, it means
the trouble indicated by that code continues to occur.
w If the buzzer does not sound when a code is being read,
it means the trouble indicated by that code occurred ear-
lier (such as poor connector contacts, etc.)
CLEARING DIAGNOSTIC CODES
1. Pull out the DOME fuse in Relay Block No. 2 for 10 sec. or
longer to clear the memory of diagnostic codes.
2. After reinserting the fuse, check that the normal code is output.
±
AIR CONDITIONING SYSTEM TroubleshootingAC±27
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DIAGNOSTIC CODE CHART
If a malfunction code is displayed during the diagnostic code check (sens\
or check), check the circuit listed for
that code in the table below (Proceed to the page given for that circuit.)\
Code No.Diag. Code Detecting Condition
00 Normal
11 *1 Open or short in room temperature sensor circuit.
12 Open or short in ambient temperature sensor circuit.
13 Open or short in evaporator temperature sensor circuit.
14*2 Open or short in water temperature sensor circuit.
21*3 Open in solar sensor circuit.
21*3
 Short in solar sensor circuit.
22*4
 All conditions below are detected for 3 secs. or more.
 (a) Engine rpm : 450 rpm or more.
 (b) Ratio between engine and compressor rpm deviates 20% or more in c\
omparison to normal
operation.
23
 Open in pressure sensor circuit.
 Abnormal refrigerant pressure below 206 kPa (2.1 kgf/cm, 30 psi)
over 2,650 kPa (27 kgf/cm, 385 ps\
i)
31 Short to ground or power source circuit in Air Mix Damper position sens\
or circuit.
32 Short to ground or power source circuit in Air Inlet Damper position se\
nsor circuit.
33 Short to ground or power source circuit in Air Outlet Damper position s\
ensor circuit.
41 Air mix damper position sensor value does not change even if ECU operat\
es air mix servomotor.
42 Air inlet damper position sensor value does not change even if ECU oper\
ates air inlet servomotor.
43 Air outlet damper position sensor value does not change even if ECU ope\
rates air outlet
servomotor.
HINT: *1 If the room temp. is approx. ±20 °C (±4 °F) or lower, code 11 may be output even though the system
is normal.
*2 If the ambient temperature is approx. ±50 °C (±58 °F) or lower, a malfunction code may be output
even though the system is normal.
*3 If the check is being performed in a dark place, diagnostic code 21 (so\
lar sensor circuit abnormal) could be displayed.
In this case, perform diagnostic code check again while shining a light,\
such as an inspection light,
on the solar sensor.
If code 21 is still displayed, there could be trouble in the solar senso\
r circuit
AC±28
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AIR CONDITIONING SYSTEM Troubleshooting
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STANDARD VALUE OF ECU TERMINAL
TerminalsSymbolsWiringColorConditionStandardValue
A14±1A14±7B ER W±BIG OFF10 ~ 14 V
A14±2 A14±3MH MCV R±YIG OFF13 ~ 19

A14±4A14±5MFRSMRECG G±RIG OFF13 ~ 19

A14±6A14±7IG+ ER±L W±BIG ON10 ~ 14 V
Body
A14±7 
Ground Body
E 
Ground Body
W±B 
GroundAlwaysBelow 1

A14±8A14±9FACE DEFW Y±LIG OFF13 ~ 19

A14±15A14±7ACC EL±R W±BTurn ignition switch ACC10 ~ 14 V
A12±2 A14±7REOST EW±G W±B
IG ON and turn headlight control SW
to TAIL position.
Turn Rheostat volume from most
right to left position.
Most
: 0 ~ 14 V
Right

Most
: 10 ~ 14 V
Left
A12 3 A14 7WV EBY WB
Start
the
MAX
Temp. Control Switch:
COLDBelow 1 V
A12±3 A14±7WV EB±Y W±Btheen-
gine MAX
Temp. Control Switch:
HOT10 ~ 14 V
A12 4 A14 7MGC ELR WB
Start the
engine andA/C switch ONBelow 1 V
A12±4 A14±7MGCEL±R W±Bengine andpush AUTO
SWA/C switch OFF10 ~ 14 V
A12 5 A14 7TC EL WBIG ONHLC SW
Rheostat Most
:
Volume RightBelow 1 V
A12±5 A14±7TCEL W±BH.L.C. SW
: TAIL positionRheostat Turn
:
Volume Left10 ~ 14 V
A12±6 A14±7TAIL EG W±BTurn the light control switch to TAILposition10 ~ 14 V
A12±7A14±7LV EYW±BIG ONPush blower SW to change
the blower speed from 1 to
10.Speed 1: 10 ~ 14 V

Speed 10: Below 2 V
A12±8 A14±7BLR EB±R W±BIG ONTurn the blower motorBelow 1.5 V
A12±9 A14±7HR EL±W W±B
IG ON
Turn the blower motorBelow 1 V
IG ONDon't turn the blower motor10 ~ 14 V
A12 10 A14 7RDFGR ERY WBIG ON
Rear defogger switch ONBelow 1 V
A12±10 A14±7RDFGR ER±Y W±BIG ONRear defogger switch OFF10 ~ 14 V
A13±1 A14±7IGN EBW±BStart the engine10 ~ 14 V
AC±32±
AIR CONDITIONING SYSTEM Troubleshooting
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99
Check voltage between terminals S5 and TS of air conditioner
control assembly connector.
(1) Remove console upper panel. (See page
BO-111 ).
(2) Remove A/C control assembly with connec-
tors still connected.
(3) Turn ignition switch ON.Measure voltage between terminals S5 and TS
of air conditioner control assembly connector
when the solar sensor is subjected to an electric
light, the sensor is covered by a cloth.
ConditionVoltage
Sensor subjected to electric light
Sensor covered by a cloth
Below 4 V
4 ±4.5 V
In addition, when the inspection light is gradu-
ally moved away from the sensor, the voltage
increases.
Proceed to next circuit inspection shown on
matrix chart (See page AC-36).However,
when Diag. code 21 is displayed, check and
replace air conditioner control assembly.
Check solar sensor.
(1) Remove solar sensor from dashboard.
(2) disconnect solar sensor connector.
Connect positive (+) lead of ohmmeter to terminal 2
and negative (±) lead to terminal 1 of the solar sensor.
(1) Cover the sensor by a cloth.
(2) Measure resistance between terminals 1 and 2 of solar sensor connector.
(1) Remove the cloth from the solar sensor andsubject the sensor to electric light.
(2) Measure resistance.
Resistance: Approx, 4 k
(continuity)
In addition, as the electric light is moved gradu-
ally away from the sensor the resistance in-
creases.
Replace solar sensor.
Check for open and short in harness and connector between air conditioner
control assembly and solar sensor (See page IN-27).
Repair or replace harness or connector.
Check and replace air conditioner control
assembly.
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±53
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Check power transistor.
(1) Remove cooling unit (See page BO-107).
(2) Disconnect power transistor connector.
(1) Check test bulb lights up when battery and
resistor are connected to power transistor
connector as left illustration shows.
(2) Measure resistance between terminal 2 and 3
(1) The bulb lights up.
(2)Resistance: 2.0± 2.4 k 
Replace power transistor.
Check for open and short in harness and connector between air
conditioner control assembly and power transistor (See page IN-27).
Repair or replace harness or connector.
Proceed to next circuit inspection shown on matrix
chart (See page AC-36).
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±79
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No.Gauge reading kPa (kgf/cm2, psi)ConditionProbable cause Remedy
LO: 1.5 ± 2.0(21 ±28, 147 ±196)
HI: 14.5 ± 15.0(206 ±213, 1422 ±1471)
Normal coolingNormally functioning
system
During operation, pressure at low
pressure side sometimes becomes a
vacuum and sometimes normal.Periodically cools
and then fails to
cool.Moisture present in
refrigeration system.(1). Replace receiver
(2). Remove moisturein system through
repeatedly
evacuating air
Inspection of Refrigeration System with Manifold Gauge Set
This is a method in which the trouble is located by using a manifold gauge s\
et. (See ºInstallation of Manifold
Gauge Setº on page AC±15) Read the manifold gauge pressure when the following conditions are es\
tablished:
(a) Temperature at the air inlet with the switch set at RECIRC is 30±35 °C (86±95 °F).
(b) Engine running at 2,000 rpm.
(c) Blower fan speed control switch set at high speed.
(d) Temperature control switch set at max. cool side.
HINT: It should be noted that the gauge indications may vary slightly due to\
ambient temperature conditions.
NOTICE:
w Always recover refrigerant before removing the parts in the refrigerant \
line and evacuating air.
w Evacuate air and charge proper amount of purified refrigerant after installing th\
e parts in the
refrigerant line.
AC±100
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AIR CONDITIONING SYSTEM Troubleshooting
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RECEIVER
ON±VEHICLE INSPECTION
1. REMOVE THE HEADLIGHT ON THE VEHICLE'S LEFTSIDE
See page BE±37
2. INSPECT FITTINGS FOR LEAKAGE Using a gas leak tester, check for leakage.
If there is leakage, check the tightening torque at the joints.
3. INSTALL HEADLIGHT See page BE±37
REMOVAL OF RECEIVER
1. REMOVE THE HEADLIGHT ON THE VEHICLE'S LEFT
SIDE
See page BE±37
2. RECOVER REFRIGERANT IN REFRIGERATION SYSTEM See page AC±16
3. REMOVE TWO LIQUID TUBES FROM RECEIVER Remove the two bolts and both the tubes from the receiver.
4. REMOVE RECEIVER FROM RECEIVER HOLDER Remove the bolt, then remove the receiver from the receiver
holder.
NOTICE: Cap the open fittings immediately to keep mois-
ture out of the system.
AC±118
±
AIR CONDITIONING SYSTEM Receiver
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INSTALLATION OF RECEIVER
1. INSTALL RECEIVER IN RECEIVER HOLDERInstall the receiver in the receiver holder with the one bolt.
2. INSTALL TWO LIQUID TUBES ON RECEIVER Install the two liquid tubes on the receiver with the two bolts.
Specified torque: 5.4 N Vm (55 kgf Vcm, 4 ft Vlbf)
NOTICE: Do not remove the caps until the tubes are con-
nected.
3. REPLENISH COMPRESSOR OIL IF RECEIVER HAS BEEN REPLACED
Add 20 cc (0.7 fl.oz.)
Compressor oil: ND OIL 6,
SUNISO NO. 5 GS or equivalent
4. EVACUATE AIR IN REFRIGERATION SYSTEM ANDCHARGE WITH REFRIGERANT
See page AC±17
Specified amount: 950 + 50 g (33.44 + 1.76 oz)
5. INSPECT FOR LEAKAGE OF REFRIGERANT
Using a gas leak tester, check for leakage of refrigerant.
If there is leakage, check the tightening torque at the joints.
6. INSPECT A/C OPERATION
7. INSTALL HEADLIGHT See page BE±37
±
AIR CONDITIONING SYSTEM ReceiverAC±119
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