Lexus SC300 / Lexus SC400. Manual - part 33

Check  voltage between terminal WV of  A/C control assembly connec-
tor body ground.

(1)

Remove console upper panel.(See page
 

BO-111

).

(2)

Remove A/C control assembly with connec–
tors still connected.

(3)

Start the engine.

Measure voltage between terminals WV of A/C con-
trol assembly connector and body ground
when the set temp. is not set to MAX COLD and
MAX HOT.

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

AC-36

).

Check water valve VSV.

Water valve VSV connector.

Measure resistance between terminals of VSV con-
nector.

Resistance:

37 – 47 

 at 20

°

C (68

°

F)

Check operation of water valve VSV when battery
voltage is applied to terminals of VSV connector or 
not.

 Battery voltage is applied:

The air from A is flowing out through B.

 Battery voltage is not applied:

The air from A is flowing out through air filter.

Replace water valve VSV.

Check for open and short in harness and connector between VSV
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–91

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Temperature Control Switch Circuit

CIRCUIT DESCRIPTION

By turning the temp. control switch, the set temperature of the
A/C can be adjusted in steps of 1

°

F (USA) or 0.5

°

C (Canada).

Turning the switch fully will set the A/C to MAX. COLD or MAX.
HOT.
The ECU calculates the set temperature from the combination
of Hi (5 V) or Low (0 V) terminals SET 1 ~ 5 of the temp. control
SW and displays the set temperature on the LCD display.
If a malfunction occurs in the temp. control SW circuit, malfunc-
tions such as not being able to set the desired temperature oc-
cur.

DIAGNOSTIC CHART

WIRING DIAGRAM

Check for  open and short in harness and
connector between A/C control assembly and
temp. control SW.

Check temp. control switch.

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

AC-36

).

Replace temp. control switch.

Repair or replace harness or

connector.

Check and replace A/C control assembly.

Check voltage between terminal SET 1 ~ 5
and SG of A/C control assembly.

AC–92

–

AIR CONDITIONING SYSTEM

Troubleshooting

Check  voltage between terminal SET 1 ~ 5 and SG of  A/C control 
assembly

(1)

Remove A/C control assembly with connec-
tors.(See page  

AC-138

).

(2)

Turn ignition switch ON.

Measure voltage between terminals SET 1 ~ 5 and
SG of temp. control switch is turned from most left to
right position.

for USA spec.

for Canada spec.

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

AC-36

).

Go to step (2).

INSPECTION PROCEDURE

–

AIR CONDITIONING SYSTEM

Troubleshooting

AC–93

Check temp. control switch.

Disconnect temp. control switch connector.

Measure resistance between terminals SET 1 ~ 5
and SG of temp. control switch is turned from most
left to right position.

for USA spec.

for Canada spec.

Replace temp. control switch.

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

IN-27

).

Repair or replace harness or connector.

Check and replace A/C control assembly.

AC–94

–

AIR CONDITIONING SYSTEM

Troubleshooting