Lexus RX300 (MCU15). Service manual — part 406
I05291
GND
M–
M+
+B
SI
DI–854
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
LEXUS RX300 (RM785E)
3
Check blower motor control relay.
PREPARATION:
Remove blower motor control relay with connectors still con-
nected.
CHECK:
(a)
Turn ignition switch ON.
(b)
Operate blower motor (High blower speed).
OK:
Terminals
Standard Value
GND ↔ Body Ground
Continuity
+B ↔ Body Ground
Battery Voltage
+M ↔ Body Ground
Battery Voltage
M+ ↔ M–
Battery Voltage
SI ↔ Body Ground
1 – 3 V
NG
Replace blower motor relay.
OK
Repair or replace harness or connector.
I08353
Engine and ECT ECU
ACMG
E10
6
LG–B
2C
2
2
1
Heater
Relay
5
3
Engine Room J/B
MG CLT Relay
2E
3
B–Y
EB1
3
A3
Compressor
Magnetic Clutch
3
B–Y
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
DI–855
LEXUS RX300 (RM785E)
Compressor Circuit
CIRCUIT DESCRIPTION
The A/C ECU (Combination meter ECU) outputs the magnetic clutch ON signal from terminal MGC to the
engine and ECT ECU. When the engine and ECT ECU receives this signal, it sends a signal from terminal
ACMG and switches the A/C magnetic clutch relay ON, thus turning the A/C compressor magnetic clutch
ON.
WIRING DIAGRAM
DI3G8–03
I08373
(–)
ACMG(+)
I05334
3
DI–856
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
LEXUS RX300 (RM785E)
INSPECTION PROCEDURE
1
Check voltage between terminal ACMG of engine and ECT ECU.
CHECK:
(a)
Start engine.
(b)
Push AUTO SW.
(c)
Measure voltage between terminal ACMG of engine and
ECT ECU connector and body ground when A/C switch
is ON and OFF.
OK:
A/C switch
Voltage
ON
10 – 4 V
OFF
0 V
OK
Check and replace engine and ECT ECU and/or
A/C ECU (Combination meter ECU).
NG
2
Check A/C compressor magnetic clutch.
PREPARATION:
Disconnect magnetic clutch connector.
CHECK:
Connect positive (+) lead connected to battery to magnetic
clutch connector terminal 3.
OK:
Magnetic clutch is energized.
NG
Repair A/C compressor magnetic clutch.
OK
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
DI–857
LEXUS RX300 (RM785E)
3
Check harness and connector between A/C compressor and compressor relay
(See page IN–32).
NG
Repair or replace harness or connector.
OK
4
Check harness and connector between compressor relay and engine and ECT
ECU (See page IN–32).
NG
Repair or replace harness or connector.
OK
5
Check harness and connector between engine and ECT ECU and A/C compres-
sor assembly (See page IN–32).
NG
Repair or replace harness or connector.
OK
Check and replace engine and ECT ECU and/
or A/C ECU (Combination meter ECU).
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