SYSTEM DESCRIPTION
=NHHA0197
Component parts
NHHA0197S01
Fan speed control system components are:
1)
Auto amp.
2)
Fan control amp.
3)
A/C LAN system (PBR built-in air mix door motor, mode door
motor and intake door motor)
4)
In-vehicle sensor
5)
Ambient sensor
6)
Sunload sensor
7)
Intake sensor
System Operation
NHHA0197S02
RHA388H
Automatic Mode
NHHA0197S03
In the automatic mode, the blower motor speed is calculated by the
automatic amplifier based on inputs from the PBR, in-vehicle
sensor, sunload sensor, intake sensor and ambient sensor. The
blower motor applied voltage ranges from approximately 5 volts
(lowest speed) to 12 volts (highest speed).
The control blower speed (in the range of 5 to 12V), the automatic
amplifier supplies a gate voltage to the fan control amplifier. Based
on this voltage, the fan control amplifier controls the voltage sup-
plied to the blower motor.
Starting Fan Speed Control
NHHA0197S04
Start Up From “COLD SOAK” Condition (Automatic mode)
NHHA0197S0401
In a cold start up condition where the engine coolant temperature
is below 50°C (122°F), the blower will not operate for a short period
of time (up to 126 seconds). The exact start delay time varies
depending on the ambient and engine coolant temperature.
In the most extreme case (very low ambient) the blower starting
delay will be 126 seconds as described above. After this delay, the
blower will operate at low speed until the engine coolant tempera-
ture rises above 55°C (131°F), at which time the blower speed will
increase to the objective speed.
GI
MA
EM
LC
EC
FE
AT
AX
SU
BR
ST
RS
BT
SC
EL
IDX
TROUBLE DIAGNOSES
Blower Motor (Cont’d)
HA-67