Air INFINITI QX56 2004 Factory Service Manual

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Blower Speed Compensation - Sunload
When the in-vehicle temperature and the set temperature are very close, the blower will be operating at low
speed. The speed will vary depending on the sunload. During conditions of low or no sunload, the blower
operates at low speed. During high sunload conditions, the front air control causes the blower speed to
increase.
Blower Speed Control Specification
COMPONENT DESCRIPTION
Variable Blower Control
The variable blower control is located on the front heater and cooling
unit. The variable blower control receives a gate voltage from the
front air control to steplessly maintain the blower motor voltage in the
0 to 5 volt range (approx.).
DIAGNOSTIC PROCEDURE FOR BLOWER MOTOR
SYMPTOM: Blower motor operation is malfunctioning under starting
blower speed control.
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ATC-86
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1. CHECK FUSES
Check 20A fuses [No. 24 and 27 (located in the fuse and fusible link box)]. For fuse layout. Refer to PG-77,
"FUSE AND FUSIBLE LINK BOX" .
OK or NG
OK >> GO TO 2.
NG >> GO TO 10.
2. CHECK FRONT BLOWER MOTOR POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect front blower motor connector M62.
3. Turn ignition switch ON.
4. Press the MODE switch to select any mode except OFF.
5. Set front fan switch to high.
6. Check voltage between front blower motor harness connector
M62 terminal 2 (W/L) and ground.
OK or NG
OK >> GO TO 12.
NG >> GO TO 3.
3. CHECK FRONT BLOWER MOTOR RELAY (SWITCH SIDE) POWER SUPPLY CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect front blower motor relay M107.
3. Check voltage between front blower motor relay harness con-
nector M107 terminals 5 (GR) and 7 (P), and ground.
OK or NG
OK >> GO TO 4.
NG >> Repair harness or connector.
4. CHECK FRONT BLOWER MOTOR RELAY
Refer to ATC-89, "
Front Blower Motor Relay" .
OK or NG
OK >> GO TO 5.
NG >> Replace front blower motor relay.
5. CHECK FRONT BLOWER MOTOR RELAY (SWITCH SIDE) CIRCUIT FOR OPEN
1. Turn ignition switch OFF.
2. Disconnect blower motor relay connector M107 and front blower
motor connector M62.
3. Check continuity between front blower motor relay harness con-
nector M107 terminals 3 (W/L) and 6 (W/L)
and front blower motor harness connector M62 terminal 2 (W/L).
OK or NG
OK >> GO TO 6.
NG >> Repair harness or connector.2 - Ground : Battery voltage should exist.
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5, 7 - Ground : Battery voltage should exist.
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3, 6 - 2 : Continuity should exist.
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6. CHECK VARIABLE BLOWER CONTROL POWER SUPPLY CIRCUIT FOR OPEN
1. Disconnect variable blower control connector M122.
2. Check continuity between front blower motor relay harness con-
nector M107 terminals 3 (W/L) and 6 (W/L), and variable blower
control harness connector M122 terminal 1 (W/L).
OK or NG
OK >> GO TO 7.
NG >> Repair harness or connector.
7. CHECK VARIABLE BLOWER CONTROL SIGNAL CIRCUIT
1. Disconnect front air control connector M49.
2. Check continuity between front air control harness connector
M49 terminal 13 (G/R) and variable blower control harness con-
nector M122 terminal 2 (G/R).
OK or NG
OK >> GO TO 8.
NG >> Repair harness or connector.
8. CHECK FRONT BLOWER MOTOR RELAY (COIL SIDE) POWER SUPPLY
1. Turn ignition switch ON.
2. Check voltage between front blower motor relay harness con-
nector M107 terminal 1 (Y/G) and ground.
OK or NG
OK >> GO TO 9.
NG >> Repair harness or connector.
9. CHECK FRONT BLOWER MOTOR RELAY (COIL SIDE) GROUND CIRCUIT
1. Turn ignition switch OFF.
2. Check continuity between front blower motor relay harness con-
nector M107 terminal 2 (R/B) and front air control harness con-
nector M49 terminal 26 (R/B).
OK or NG
OK >> Replace front air control. Refer to ATC-135, "FRONT
AIR CONTROL" .
NG >> Repair harness or connector.3, 6 - 1 : Continuity should exist.
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13 - 2 : Continuity should exist.
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1 - Ground : Battery voltage should exist.
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2 - 26 : Continuity should exist.
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10. REPLACE FUSES
1. Replace fuses.
2. Activate the front blower motor.
3. Do fuses blow?
YES or NO
YES >> GO TO 11.
NO >> Inspection End.
11 . CHECK FRONT BLOWER MOTOR POWER SUPPLY CIRCUIT FOR SHORT
1. Turn ignition switch OFF.
2. Disconnect variable blower control connector M122.
3. Check continuity between variable blower control harness con-
nector M122 terminal 1 (W/L) and ground.
OK or NG
OK >> GO TO 12.
NG >> Repair harness or connector.
12. CHECK VARIABLE BLOWER CONTROL SIGNAL CIRCUIT
1. Disconnect front air control connector M49.
2. Check continuity between front air control harness connector
M49 terminal 13 (G/R) and variable blower control harness con-
nector M122 terminal 2 (G/R).
OK or NG
OK >> Check blower motor, if OK replace variable blower con-
trol. Refer to ATC-89, "
Front Blower Motor" .
NG >> Repair harness or connector.1 - Ground. : Continuity should not exist.
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13 - 2 : Continuity should exist.
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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
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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

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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.
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ATC-96
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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
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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
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Terminal No.
Continuity
Rear fan switch (front) Rear fan switch (rear)
39
Should exist 56
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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