2004 INFINITI QX56 Air

TROUBLE DIAGNOSIS
ATC-91
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Revision: August 20072004 QX56
SYSTEM DESCRIPTION
Component Parts
Rear blower speed control system components are:

Front air control

Rear fan switch (front)

Rear fan switch (rear)

Rear blower motor resistor

Rear blower motor

Rear blower motor relay
System Operation
NOTE:
The rear heat or A/C cannot operate unless the front heat or A/C is on.
Rear Blower Control
When the rear fan switch (front) is in the off (O) position, the rear blower motor cannot operate.
When the rear fan switch (front) is in the rear (R) position, it allows the rear fan switch (rear) to control the rear
blower motor speed. In any other position (1-4), the rear fan switch (front) controls the rear blower motor
speed regardless of the rear fan switch (rear) position.
DIAGNOSTIC PROCEDURE FOR REAR BLOWER MOTOR
Rear Fan Switch (Rear) Circuit
SYMPTOM:

Rear blower motor does not rotate when rear fan switch (front) is set to rear (R) position.
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ATC-92
TROUBLE DIAGNOSIS
Revision: August 20072004 QX56
1. CHECK REAR BLOWER MOTOR OPERATION
Blower motor rotates normally when rear fan switch (front) is set at 1 - 4 speed.
OK or NG
OK >> GO TO 2.
NG >> Refer to AT C - 9 3 , "
Trouble Diagnosis Procedure For Rear Blower Motor (1 - 4 Speed)" .
2. CHECK REAR FAN SWITCH (FRONT)
Refer to ATC-99, "
Rear Fan Switch (Front)" .
OK or NG
OK >> GO TO 3.
NG >> Replace rear fan switch (front). Refer to ATC-135, "
FRONT AIR CONTROL"
3. CHECK REAR FAN SWITCH (REAR)
Refer to ATC-99, "
Rear Fan Switch (Rear)" .
OK or NG
OK >> GO TO 4.
NG >> Replace rear fan switch (rear). Refer to ATC-135, "
REAR AIR CONTROL" .
4. CHECK CIRCUIT CONTINUITY
1. Turn ignition switch OFF.
2. Disconnect rear fan switch (front) connector M52 and rear fan
switch (rear) (Rear air control) connector R208.
3. Check voltage between rear fan switch (front) harness connec-
tor M52 terminal 2 (BR) and rear fan switch (rear) (Rear air con-
trol) harness connector R208 terminal 10 (BR).
OK or NG
OK >> Inspection End.
NG >> Repair harness or connector.2 - 10 : Continuity should exist.WJIA0794E

TROUBLE DIAGNOSIS
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Revision: August 20072004 QX56
6. CHECK REAR BLOWER MOTOR RELAY (COIL SIDE) POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect fuse block (J/B) connector M39.
3. Turn ignition switch ON.
4. Set rear fan switch (front) to any position except off (0), rear (R),
or 4 - speed.
5. Check voltage between fuse block (J/B) harness connector M39
terminal 3Q (W/L) and ground.
OK or NG
OK >> GO TO 7.
NG >> GO TO 20.
7. CHECK REAR BLOWER MOTOR RELAY (COIL SIDE) GROUND CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect fuse block (J/B) connector M3.
3. Check continuity between fuse block (J/B) harness connector
M3 terminal 7N (B) and ground.
OK or NG
OK >> Replace fuse block (J/B).
NG >> Repair harness or connector.
8. REPLACE FUSE
Refer to PG-76, "
FUSE BLOCK-JUNCTION BOX(J/B)" .
Fuse should not open when rear blower motor is activated.
OK or NG
OK >> Inspection End.
NG >> GO TO 9.
9. CHECK REAR BLOWER MOTOR POWER SUPPLY CIRCUIT FOR SHORT
1. Turn ignition switch OFF.
2. Disconnect battery cables and rear blower motor connector
B134.
3. Check continuity between rear blower motor harness connector
B134 terminal 2 (L/R) and ground.
OK or NG
OK >> Check rear blower motor. Refer to ATC-100, "Rear
Blower Motor" .
NG >> Repair harness or connector.1 - Ground : Battery voltage should exist.
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7N - Ground : Continuity should exist.
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2 - Ground : Continuity should not exist.
WJIA0598E

ATC-96
TROUBLE DIAGNOSIS
Revision: August 20072004 QX56
10. CHECK REAR BLOWER MOTOR RELAY (SWITCH SIDE) POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect fuse block (J/B) connector M3 and rear blower motor
connector B134.
3. Check continuity between fuse block (J/B) harness connector
M3 terminal 3N (SB) and 8N (L/R) and rear blower motor har-
ness connector B134 terminal 2 (L/R).
OK or NG
OK >> GO TO 20.
NG >> Repair harness or connector.
11 . CHECK REAR BLOWER MOTOR
Refer to ATC-100, "
Rear Blower Motor" .
OK or NG
OK >> GO TO 12.
NG >> Replace rear blower motor. Refer to ATC-141, "
REAR BLOWER MOTOR" .
12. CHECK REAR FAN SWITCH (FRONT)
Refer to ATC-99, "
Rear Fan Switch (Front)" .
OK or NG
OK >> GO TO 15.
NG >> Replace rear fan switch (front). Refer to ATC-135, "
FRONT AIR CONTROL" .
13. CHECK REAR BLOWER MOTOR RESISTOR
Refer to ATC-100, "
Rear Blower Motor Resistor" .
OK or NG
OK >> GO TO 14.
NG >> Replace rear blower motor resistor. Refer to ATC-156, "
Removal and Installation" .
14. CHECK REAR FAN SWITCH (FRONT) CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect rear fan switch (front) M52.
3. Reconnect rear blower motor resistor harness connector B133.
4. Turn ignition switch ON.
5. Check voltage between each rear fan switch (front) connector
M52 terminals 3 (LG), 7 (W/L), and 8 (G), and ground.
OK or NG
OK >> GO TO 17.
NG >> GO TO 16.3N, 8N - 2 : Continuity should exist.
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Te r m i n a l N o .
Voltage
(Approx.)
(+) (-)
3
Ground 12V 7
8
LJIA0108E

TROUBLE DIAGNOSIS
ATC-97
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Revision: August 20072004 QX56
15. CHECK REAR BLOWER MOTOR GROUND CIRCUIT TO REAR BLOWER MOTOR RESISTOR
1. Turn ignition switch OFF.
2. Disconnect rear blower motor connector B134 and rear blower
motor resistor connector B133.
3. Check continuity between rear blower motor connector B134
terminal 1 (L/B) and rear blower motor resistor harness connec-
tor B133 terminal 3 (L/B).
4. Check continuity between rear blower motor connector B134
terminal 1 (L/B) and ground.
OK or NG
OK >> GO TO 16.
NG >> Repair harness or connector.
16. CHECK REAR FAN SWITCH (FRONT) CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect rear fan switch (front) connector M52.
3. Check continuity between rear fan switch (front) connector M52
terminals 3 (LG), 7 (W/L), and 8 (G), and rear blower motor
resistor connector B133 terminals 1 (LG), 4 (W/L), and 2 (G).
OK or NG
OK >> Inspection End.
NG >> Repair harness or connector.
17. CHECK REAR FAN SWITCH (FRONT) CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect rear fan switch (rear) (Rear air control) connector
R208.
3. Check continuity between rear fan switch (front) connector M52
terminals 3 (LG), 5 (L/B), 7 (W/L), and 8 (G), and rear fan switch
(rear) (Rear air control) connector R208 terminals 9 (LG), 6 (L/
B), 8 (W/L), and 7 (G).
OK or NG
OK >> GO TO 18.
NG >> Repair harness or connector.1 - 3 : Continuity should exist.
1 - Ground : Continuity should not exist.
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Te r m i n a l N o .
Continuity
Rear fan switch (front) Rear blower motor resistor
31
Should exist 74
82
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Terminal No.
Continuity
Rear fan switch (front) Rear fan switch (rear)
39
Should exist 56
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WJIA0799E

ATC-98
TROUBLE DIAGNOSIS
Revision: August 20072004 QX56
18. CHECK REAR FAN SWITCH (FRONT)
Refer to ATC-99, "
Rear Fan Switch (Front)" .
OK or NG
OK >> GO TO 19.
NG >> Replace rear fan switch (front). Refer to ATC-135, "
FRONT AIR CONTROL" .
19. CHECK REAR FAN SWITCH (REAR)
Refer to ATC-99, "
Rear Fan Switch (Rear)" .
OK or NG
OK >> Inspection End.
NG >> Replace rear fan switch (rear). Refer to ATC-135, "
REAR AIR CONTROL" .
20. CHECK CIRCUIT BETWEEN FRONT AIR CONTROL AND FUSE BLOCK (J/B) [REAR BLOWER
MOTOR RELAY (COIL SIDE) POWER]
1. Disconnect front air control connector M50 and fuse block (J/B)
connector M39.
2. Check continuity between front air control harness connector
M50 terminal 38 (W/L) and fuse block (J/B) connector M39 ter-
minal 3Q (W/L).
OK or NG
OK >> Replace front air control. Refer to ATC-135, "FRONT
AIR CONTROL"
NG >> Repair harness or connector.38 - 3Q : Continuity should exist.LJ IA 0 111E

TROUBLE DIAGNOSIS
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Revision: August 20072004 QX56
Rear Air Control CircuitEJS002CK
SYMPTOM:

Temperature cannot be adjusted from the rear air control.
INSPECTION FLOW
*1ATC-59, "Operational Check (Rear)"*2AT C - 5 3 , "A/C System Self-diagno-
sis Function"
*3AT C - 5 5 , "SELF-DIAGNOSIS CODE
CHART"
*4ATC-102, "DIAGNOSTIC PROCE-
DURE FOR REAR AIR CONTROL"
*5AT C - 7 3 , "DIAGNOSTIC PROCE-
DURE FOR AIR MIX DOOR
MOTOR (REAR)"
WJIA0801E

ATC-102
TROUBLE DIAGNOSIS
Revision: August 20072004 QX56
SYSTEM DESCRIPTION
Component Parts
Rear air control system components are:

Front air control

Rear air control

Air mix door motor (rear)

Rear blower motor relay

Rear blower motor resistor

Rear blower motor
System Operation
Rear Air Control
When the rear fan switch (front) (integral to the front air control) is in the rear (R) position the rear blower motor
speeds and the rear temperature/mode are controlled by the rear fan switch (rear) and the rear temperature/
mode dial (rear) (both integral to the rear air control).
DIAGNOSTIC PROCEDURE FOR REAR AIR CONTROL
SYMPTOM:

Blower motor operation is malfunctioning. Refer to ATC-90, "Rear Blower Motor Circuit" .

Temperature/mode operation is malfunctioning.
1. CHECK OPERATION FROM FRONT AIR CONTROL
Does rear temperature/mode operate normally from front air control?
YES or NO
YES >> GO TO 2.
NO >> Refer to AT C - 7 3 , "
DIAGNOSTIC PROCEDURE FOR AIR MIX DOOR MOTOR (REAR)" .
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