1991 LEXUS SC400 diagram

Location of Connectors in Engine Compartment
wLocation of connectors
This diagram shows the wire harnesses and connectors used in one system.\
The connector shows the harness side connector, so when checking the part side connector (sensor, ac-
tuator, etc.), be careful not to mistake the terminal positions.
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DIAGNOSIS SYSTEM
Warning for A/C compressor lock
If compressor lock occurs during air conditioner operation, the
( A/C ) switch indicator on the air conditioner control assembly
starts blinking to warn the driver.
When this occurs, check for compressor lock (code 22) using diag-
nostic code check then proceed to inspect the circuit or the com-
ponent.
Compressor lock sensor circuit page AC±54.
LIST OF OPERATION METHODS
By operating each of the air conditioner control switches as shown in the \
diagram below, it is possible to enter
the diagnosis check mode. AC±26
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WIRING DIAGRAM
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9
Check voltage between terminals LP of air conditioner control
assembly and body ground.
(1) Install the manifold gauge set.(See page AC-15).
(2) Turn ignition switch ON.
Check voltage between terminals LP of air conditioner
control assembly connector and body ground when the
air conditioner gas pressure is
changed.
The voltage changes with gas pressure, as shown
in the diagram below.
Low Pressure Cut Side
High pressure Cut Side
Proceed to next circuit inspection shown on
matrix chart (See page AC-36).
Check pressure switch.
Disconnect pressure switch connector.
Check continuity between terminals 1 and 4 of pres-
sure switch when air conditioner gas pressure is
changed.
The continuity changes with gas pressure as
shown below.
Low Pressure Cut Side
High pressure Cut Side
Replace pressure switch
Check for open and short in harness and connector between air conditioner control
assembly and pressure switch, pressure switch and body ground (See page IN-27).
Repair or replace harness or connector.
Check and replace air conditioner control
assembly.
INSPECTION PROCEDURE
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IG Power Source Circuit
CIRCUIT DESCRIPTION
This is the power source for the air conditioner control assembly (contains\
the A/C control assembly)
and servomotor, ect.
DIAGNOSTIC CHART
WIRING DIAGRAM
Check voltage between terminals IG+ and E
of air conditioner control assembly
connector.
Check continuity between terminal E of air
conditioner control assembly and
body ground.
Check HTR fuse.
Check harness and repair and connector be-
tween air conditioner control assembly and
battery
Proceed to next circuit inspection
shown on matrix chart (See page
AC-36).
Check for short in all the harness
and components connected to
the HTR fuse (See attached wir -
ing diagram).
Repair or replace harness or
connector.
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Check voltage between terminals IG+ and E of air conditioner control
assembly connector.
(1) Remove console upper panel.(See pageBO-111 ).
(2) Remove A/C control assembly with connec±
tors still connected.
(3) Turn ignition switch ON.
Measure voltage between terminals IG+ and E of air
conditioner control assembly.
Voltage: 10 ±14 V
Proceed to next circuit inspection shown on matrix
chart (See page AC-36).
Check continuity between terminals E of air conditioner control assem-
bly and body ground.
Measure resistance between terminals E of air condi-
tioner control assembly and body ground.
Resistance:1  or less
Repair or replace harness or connector.
Remove HTR fuse from J/B No. 1.
Check continuity of HTR fuse
Continuity
Check HTR fuse.
Check for short in all the harness and
components connected to the HTR fuse
See attached wiring diagram).
Check and repair harness and connector between air conditioner control \
assembly and battery.
INSPECTION PROCEDURE
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ACC Power Source Circuit
CIRCUIT DESCRIPTION
This circuit supplies power to the air conditioner control assembly (contai\
ns the A/C control assembly).
DIAGNOSTIC CHART
WIRING DIAGRAM
Check voltage between terminals ACC of air
conditioner control assembly connector
and body ground.
Check RADIO No. 2 fuse.
Check and repair harness and connector
between air conditioner control assembly
and battery.
Proceed to next circuit inspection
shown on matrix chart (See page
AC-36).
Check for short in all the harness
and components connected to
the RADIO No. 2 fuse (See
attached wiring diagram).
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Check voltage between terminals ACC of air conditioner control
assembly connector and body ground.
(1) Remove console upper panel.(See page BO-111 ).
(2) Remove A/C control assembly with connec±
tors still connected.
(3) Turn ignition switch ON.
Measure voltage between terminals ACC of air
conditioner control assembly connector and body
ground.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix
chart (See page AC-36).
Check RADIO No. 2 fuse.
Remove RADIO No. 2 fuse from J/B No. 1.
Check continuity of RADIO No. 2 fuse.
Continuity.
Check for short in all the harness and
components connected to the RADIO No. 2
fuse (See attached wiring diagram).
Check and repair harness and connector between air conditioner control \
assembly and battery.
INSPECTION PROCEDURE
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