Lexus SC300 / Lexus SC400. Manual - part 34

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Automatic Control Switch Circuit

CIRCUIT DESCRIPTION

The SW contact is ON while the automatic control SW is pushed, and
turns OFF when automatic control SW is released. When the SW is
turned ON, the voltage at the SAUTO terminal of A/C control assem-
bly is almost 0 V and the ECU begins fully automatic control of the
blower speed, air inlet, air outlet and compressor operation.

DIAGNOSTIC CHART

Check voltage between terminal SAUTO

and SG of A/C control assembly.

Check automatic control SW.

Check for open and short in harness and
connector between automatic control SW
and ECU.

Check and replace A/C control assembly.

Proceed to next circuit inspection on

matrix chart(See    page 

AC-36

).

Replace automatic control SW.

Repair or replace harness or

connector.

AC–96

–

AIR CONDITIONING SYSTEM

Troubleshooting

Check  voltage between terminal SAUTO and SG of A/C control
assembly.

(2)

Remove A/C control assembly with connectors
still connected.

Proceed to next circuit inspection shown on
matrix chart. ( See page 

AC-36

).

(3)

Turn ignition switch on.

(1)

Remove console upper panel. (See page 

BO–111

).

Measure voltage between terminal SAUTO and Sg
of A/C control assembly when automatic control SW
is operated.

Disconnect automatic control switch connector.

Measure resistance between terminal and of auto-
matic control switch connector when it is is 
operated.

Replace automatic control switch.

Check automatic control switch.

Check for open and short in harness and connector between switch and
A/C control assembly (See page 

IN-27

).

Repair or replace harness or connector.

Check and replace A/C control assembly.

INSPECTION PROCEDURE

–

AIR CONDITIONING SYSTEM

Troubleshooting

AC–97

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Diagnosis Circuit

CIRCUIT DESCRIPTION

This circuit sends signals to the A/C control assembly requesting output of diagnostic codes.

DIAGNOSTIC CHART

WIRING DIAGRAM

Check voltage between terminals Tc and
E1 of TDCL.

Check harness and connector between air

conditioner control assembly and TDCL and

body ground.

Proceed to next circuit inspection

shown on matrix chart (See page

AC-36

).

Repair or replace harness or

connector.

Check and replace air conditioner control

assembly.

AC–98

–

AIR CONDITIONING SYSTEM

Troubleshooting

Check  voltage between terminal Tc and E1 of TDCL.

(2)

Check voltage between terminals Tc and E1 of 
TDCL.

Voltage:

10 – 14 V

(1)

Turn ignition switch on.

Proceed to next circuit inspection shown on
matrix chart. ( See page 

AC-36

).

Check for open and short in harness and connector between air conditioner con-
trol assembly and TDCL, TDCL and body ground.(See page 

IN-27

).

Repair or replace harness or connector.

Check and replace air conditioner control

assembly.

INSPECTION PROCEDURE

–

AIR CONDITIONING SYSTEM

Troubleshooting

AC–99