1991 LEXUS SC300 ect

Trouble AreaMemory*5See page
±±±
 Room temp. Sensor
 Harness or connector between room temp. sensor and A/C control assembly\
 A/C control assemblyO
(8.5 min. or more)AC±44
 Ambient temp. sensor
 Harness or connector between ambient temp. sensor and A/C control assem\
bly
 A/C control assemblyO
(8.5 min. or more)AC±46
 Evaporator temp. sensor
 Harness or connector between evaporator temp. sensor and A/C control
assembly A/C control assemblyO
(8.5 min. or more)AC±48
 Water temp. sensor
 Harness or connector between water temp. sensor and A/C control assembl\
y
 A/C control assemblyO
(8.5 min. or more)AC±50
 Solar sensor
H b d A/C l bl
±
AC 52 Solar sensor
 Harness or connector between sensor and A/C control assembly
 A/C control assemblyOAC±52
 A/C control assemblyO
(8.5 min. or more)
 Compressor drive belt Compressor lock sensor Compressor
 Harness and connector between A/C control assembly and compressor,
 compressor lock sensor
 A/C control assembly
±AC±54
 Pressure switch
 Harness or connector between pressure switch and A/C control assembly
 Refrigerant pipe line
 A/C control assembly
±AC±56
 Air mix damper position sensor A/C control assembly
 Harness or connector between air mix damper position sensor and
A/C control assemblyO
(1 min. or more)AC±58
 Air inlet damper position sensor A/C control assembly
 Harness or connector between air inlet damper position sensor and
A/C control assemblyO
(1 min. or more)AC±62
 Air outlet damper position sensor A/C control assembly
 Harness or connector between air outlet damper position sensor and
A/C control assemblyO
(1 min. or more)AC±66
 Air mix servomotor Air mix damper position sensor
 Harness and connector between A/C control assembly and air mix position\
sensor
 Harness and connector between A/C control assembly and air mix servomot\
or.O
(15 secs. or more)AC±58
AC±60
 Air inlet servomotor Air inlet damper position sensor
 Harness and connector between A/C control assembly and air inlet positi\
on sensor.
 Harness and connector between A/C control assembly and air inlet servom\
otor.O
(15 secs. or more)AC±62
AC±64
 Air outlet servomotor Air outlet damper position sensor
 Harness and connector between A/C control assembly and air outlet posit\
ion
sensor.
 Harness and connector between A/C control assembly and air outlet servo\
motor.
 A/C control assembly
O
(15 secs. or more)AC±66
AC±68
±
AIR CONDITIONING SYSTEM TroubleshootingAC±29
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AC±68AC±70AC±72AC±74AC±76AC±78AC±80AC±82AC±84AC±90AC±92AC±96AC±98AC±10
8IN±32AC±100AC±103AC±10
4AC±12
0AC±118AC±122AC±12
5AC±126
HINT:
wIf the instruction ºProceed to next circuit inspection shown on matrix \
chartº is given in the flow chart for each
circuit, proceed to the circuit with the next highest number in the table to con\
tinue the check.
w If the trouble still reappears even though there are no abnormalities in a\
ny of the other circuits, then check
or replace the air conditioner control assembly (contains the ECU).
±
AIR CONDITIONING SYSTEM TroubleshootingAC±37
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LOCATION OF CONNECTORS
LOCATION OF CONNECTORS IN ENGINE COMPARTMENT
AC±38±
AIR CONDITIONING SYSTEM Troubleshooting
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LOCATION OF CONNECTORS IN INSTRUMENT PANEL
AC±40±
AIR CONDITIONING SYSTEM Troubleshooting
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LOCATION OF CONNECTORS IN INSTRUMENT PANEL
AC±42±
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Check voltage between terminals TR
and SG of air conditioner assembly
connector.
Check room temperature sensor.
Check harness and connector between air
conditioner control assembly and room tem-
perature sensor (See page IN-27).
Check and repair air conditioner control
assembly. Proceed to next circuit inspection
shown on matrix chart (See page
AC-36
).However, when Diag. code
11 is displayed, check and replace
air conditioner control assembly.
Replace room temperature sensor.
Repair or replace harness or
connector.
CIRCUIT INSPECTION
Diag. Code 11Room Temperature Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the temperature inside the cabin and sends the appropria\
te signals the A/C control
assembly.
Code No.Diag. Code Detecting ConditionTrouble area
11
Open or short in room temperature sensor
circuit.
Room temperature sensor.

Harness or connector between room temp.
sensor and A/C control assembly.

A/C control assembly.
DIAGNOSTIC CHART
AC±44±
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Check voltage between terminals TR and SG of air conditioner control
assembly connector.
(1) Remove console upper panel. (See page BO-111 )
(2) Remove A/C Control Assembly with connectors
still connected.
(3) Turn ignition switch ON.
Check voltage between terminals TAM and SG of air
conditioner control assembly connector at each tem-
perature.
Voltage
at 25°C (77°F) : 1.8~2.2 V
at 40°C (104°F) : 1.2~1.6 V
In addition, as the temperature increases, the
voltage decreases gradually.
Proceed to next circuit inspection shown on
matrix chart (See page AC-36).However,
when Diag. code 11 is displayed, check and
replace air conditioner control assembly.
Check room temperature sensor.
(1) Remove instrument finish lower No. 1 panel.
(See page Be-103).
Resistance
at 25°C (77°F) : 1.6~1.8k

at 50°C (122°F) : 0.5~0.7k

In addition, as the temperature increases, the
voltage decreases gradually.
Replace room temperature sensor.
Check for open and short in harness and connector between air conditioner
control assembly and room temperature sensor (See page IN-27).
Repair or replace harness or connector.
Check and repair air conditioner control
assembly.
(2) Disconnect room0 temperature sensor
connector.
Check voltage between terminals 1 and 2 of
room temperature sensor connector at each tem±
perature.
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±45
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Diag. Code 12Ambient Temperature Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the ambient temperature and sends the appropriate signal\
s to the A/C control
assembly.
Code No.Diag. Code Detecting ConditionTrouble area
12
Open or short in ambient temperature sensor
circuit.
Ambient temperature sensor.

Harness or connector between ambient
temperature sensor and A/C control assem-
bly.

A/C control assembly.
DIAGNOSTIC CHART
Check voltage between terminals TAM and
SG of air conditioner control assembly con-
nector.
Check ambient temperature sensor.
Check harness and connector between air
conditioner control assembly and ambient
temperature sensor. (See page IN-27).
Check and replace air conditioner control
assembly.
Proceed to next circuit inspection
shown on matrix chart (See
pageAC-36 ). However, when Diag.
code 12 is displayed, check and re-
place air conditioner control assembly.
Replace ambient temperature
sensor.
Repair or replace harness or
connector.
AC±46±
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