Infiniti QX4 (R50). Manual — part 475
Blower Speed Compensation
NBHA0062S05
Sunload
NBHA0062S0501
When the in-vehicle temperature and the set temperature are very close, the blower will be operating at low
speed. The low speed will vary depending on the sunload. During conditions of high sunload, the blower low
speed is “normal” low speed (approx. 6V). During low or no sunload conditions, the low speed will drop to “low”
low speed (approx. 5V).
Ambient
NBHA0062S0502
When the ambient temperature is in the “moderate” range [10 - 15°C (50 - 59°F)], the computed blower volt-
age will be compensated (reduced) by up to 3.5V (depending on the blower speed). In the “extreme” ambi-
ent ranges [below 0°C (32°F) and above 20°C (68°F)] the computed objective blower voltage is not compen-
sated at all. In the ambient temperature ranges between “moderate” and “extreme” [0 - 10°C (32 - 50°F) and
15 - 20°C (59 - 68°F)], the amount of compensation (for a given blower speed) varies depending on the ambi-
ent temperature.
Fan Speed Control Specification
NBHA0062S06
RHA138G
RHA648F
COMPONENT DESCRIPTION
NBHA0063
Fan Control Amplifier
NBHA0063S01
The fan control amplifier is located on the cooling unit. The fan
control amp. receives a gate voltage from the auto amp. to step-
lessly maintain the blower fan motor voltage in the 5 to 12 volt
range (approx.).
RHA467G
DIAGNOSTIC PROCEDURE
NBHA0064
SYMPTOM: Blower motor operation is malfunctioning under
Starting Fan Speed Control.
TROUBLE DIAGNOSES
Blower Motor (Cont’d)
HA-98
1
CHECK POWER SUPPLY FOR FAN CONTROL AMP.
Disconnect fan control amp. harness connector.
Do approx. 12 volts exist between fan control amp. harness terminal No. 3 and body ground?
RHA480G
Yes or No
Yes
©
GO TO 2.
No
©
GO TO 8.
2
CHECK BODY GROUND CIRCUIT FOR FAN CONTROL AMP.
Does continuity exist between fan control amp. harness terminal No. 1 and body ground?
RHA089G
Yes or No
Yes
©
Reconnect fan control amp. harness connector. And GO TO 3.
No
©
Repair harness or connector.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
SC
EL
IDX
TROUBLE DIAGNOSES
Blower Motor (Cont’d)
HA-99
3
CHECK VOLTAGE FOR FAN CONTROL AMP.
Set up Self-diagnosis STEP 4.
Measure voltage across fan control amp. harness terminal No. 2 and body ground.
RHA481GB
MTBL0465
OK or NG
OK
©
GO TO 5.
NG
©
I
The result is less than 2.5V. Replace fan control amp.
I
The result is more than 3.0V. GO TO 4.
4
CHECK FAN CONTROL AMP.
Refer to HA-103.
OK or NG
OK
©
GO TO 5.
NG
©
1. Replace fan control amp.
2. Go to “STEP-BY-STEP PROCEDURE”, HA-45 and perform self-diagnosis STEP 4.
Confirm that blower motor operation is normal.
5
CHECK FAN CONTROL AMP. CIRCUIT BETWEEN FAN CONTROL AMP. AND AUTO AMP. (LCU)
1. Disconnect auto amp. (LCU) and fan control amp. harness connector.
2. Check circuit continuity between auto amp. (LCU) harness terminal No. 35 and fan control amp. harness terminal No.
2.
RHA824H
Continuity should exist.
If OK, check harness for short.
OK or NG
OK
©
GO TO 6.
NG
©
Repair harness or connector.
TROUBLE DIAGNOSES
Blower Motor (Cont’d)
HA-100
6
CHECK FAN FEED BACK CIRCUIT
Reconnect auto amp. (LCU) harness connector.
Do approx. 12 volts exist between auto amp. (LCU) harness terminal No. 33 and body ground?
RHA825H
Yes or No
Yes
©
GO TO 7.
No
©
Check power supply circuit and 15A fuses (Nos. 1 and 2, located in the fuse block).
Refer to EL-14, “Wiring Diagram — POWER —”.
I
If OK, check for open circuit in wiring harness.
Repair or replace as necessary.
I
If NG, replace fuse and check wiring harness for short circuit.
Repair or replace as necessary.
7
CHECK POWER SUPPLY FOR AUTO AMP.
Do approx. 12 volts exist between auto amp. harness terminal No. 34 and body ground?
RHA826H
Yes or No
Yes
©
1. Replace auto amp.
2. Go to self-diagnosis step-by-step procedure (HA-45) and perform self-diagnosis STEP
4.
Confirm that blower motor operation is normal.
No
©
GO TO 10.
GI
MA
EM
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
SC
EL
IDX
TROUBLE DIAGNOSES
Blower Motor (Cont’d)
HA-101
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