Lexus SC300 / Lexus SC400. Manual — part 23
Diag. Code 14
Water Temperature Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the coolant temperature and sends the appropriate signals to the air conditioner
control assembly. These signals are used for warm up control when the engine is cold.
Code No.
Diag. Code Detecting Condition
Trouble area
14
Open or short in water temperature sensor
circuit.
Water temperature sensor.
Harness or connector between water
temperature sensor and A/C control as-
sembly.
A/C control assembly.
DIAGNOSTIC CHART
Check voltage between terminals TW and
SG air conditioner control assembly con-
nector.
Check water temperature sensor.
Check harness and connector between air
conditioner control assembly and water tem-
perature sensor.(See page
).
Check and replace air conditioner control
assembly.
Proceed to next circuit inspection
shown on matrix chart (See page
). However, when Diag. code
14 is displayed, check and replace
air conditioner control assembly.
Replace water temperature
sensor.
Repair or replace harness or
connector.
AC–50
–
AIR CONDITIONING SYSTEM
Troubleshooting
Check voltage between terminals TW and SG of air conditioner control
assembly connector.
(1)
Remove console upper panel. (See page
(2)
Remove A/C Control Assembly with connectors
still connected.
(3)
Turn ignition switch ON.
Measure voltage between terminals TW and SG of air
conditioner control assembly connector at each tem-
perature.
Voltage
at 0
°
C (32
°
F) : 2.8~3.2 V
at 40
°
C (104
°
F) : 1.8~2.2 V
at 70
°
C (158
°
F) : 0.9~1.3 V
In addition, as the temperature increases, the
voltage decreases gradually.
Proceed to next circuit inspection shown on
matrix chart (See page
when Diag. code 14 is displayed, check and
repair air conditioner control assembly.
Check water temperature sensor.
(1)
Remove heater unit.
(2)
Remove water temperature sensor.
Measure resistance between terminals 1 and 3 of
water temperature sensor connector at each temper-
ature.
Resistance
at 0
°
C (32
°
F) : 16.5~17.5 k
at 40
°
C (104
°
F) : 2.4~2.8 k
at 70
°
C (158
°
F) : 0.7~1.0 k
In addition, as the temperature increases, the
voltage decreases gradually.
Replace water temperature sensor.
Check for open and short in harness and connector between air conditioner
control assembly and water temperature sensor (See page
).
Repair or replace harness or connector.
Check and replace air conditioner control
assembly.
INSPECTION PROCEDURE
–
AIR CONDITIONING SYSTEM
Troubleshooting
AC–51
Diag. Code 21
Solar Sensor Circuit
CIRCUIT DESCRIPTION
A photo diode in the solar sensor detects solar
radiation and sends signals to the air conditioner
control assembly.
Code No.
Diag. Code Detecting Condition
Trouble area
21
Open or short in solar sensor circuit. (Please
note that display of diagnostic code 21 is not
abnormal when the sensor is not receiving
solar radiation)
Solar sensor.
Harness or connector between solar sensor
and A/C control assembly.
A/C control assembly.
DIAGNOSTIC CHART
Check voltage between terminals S5
and TS of air conditioner control as-
sembly connector.
Check solar sensor.
Check harness and connector between air
conditioner control assembly and solar sen-
sor (See page
Check and replace air conditioner control
assembly.
Proceed to next circuit inspection
shown on matrix chart (See page
). However, when Diag. code
21 is displayed, check and replace
air conditioner control assembly.
Replace solar sensor.
Repair or replace harness or
connector.
AC–52
–
AIR CONDITIONING SYSTEM
Troubleshooting
9
9
Check voltage between terminals S5 and TS of air conditioner
control assembly connector.
(1)
Remove console upper panel. (See page
(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.
Condition
Voltage
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
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 and
subject 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
Repair or replace harness or connector.
Check and replace air conditioner control
assembly.
INSPECTION PROCEDURE
–
AIR CONDITIONING SYSTEM
Troubleshooting
AC–53
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