Lexus SC300 / Lexus SC400. Service manual - part 21

LOCATION OF CONNECTORS IN INSTRUMENT PANEL

AC–42

–

AIR CONDITIONING SYSTEM

Troubleshooting

–

AIR CONDITIONING SYSTEM

Troubleshooting

AC–43

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 11

Room Temperature Sensor Circuit

CIRCUIT DESCRIPTION

This sensor detects the temperature inside the cabin and sends the appropriate signals the A/C control
assembly.

Code No.

Diag. Code Detecting Condition

Trouble 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

–

AIR CONDITIONING SYSTEM

Troubleshooting

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

Troubleshooting

AC–45