Air mix door control (Automatic temperature control)
The air mix door is automatically controlled so that in-vehicle temperature is maintained at a predetermined
value by: The temperature setting, ambient temperature, in-vehicle temperature and amount of sunload.
Fan speed control
Blower speed is automatically controlled based on temperature setting, ambient temperature, in-vehicle
temperature, intake temperature, amount of sunload and air mix door position.
With FAN switch set to ``AUTO'', the blower motor starts to gradually increase air ¯ow volume.
When engine coolant temperature is low, the blower motor operation is delayed to prevent cool air from ¯ow-
ing.
Intake door control
The intake doors are automatically controlled by: The temperature setting, ambient temperature, in-vehicle
temperature, intake temperature, amount of sunload and ON-OFF operation of the compressor.
Outlet door control
The outlet door is automatically controlled by: The temperature setting, ambient temperature, in-vehicle
temperature, intake temperature and amount of sunload.
Magnet clutch control
The ECM (ECCS control module) controls compressor operation using input signals from the throttle position
sensor and auto ampli®er.
Self-diagnostic system
The self-diagnostic system is built into the auto ampli®er (LCU) to quickly locate the cause of problems.
RHA442G
DESCRIPTIONAUTO
Features (Cont'd)
HA-51
SYSTEM DESCRIPTION
Component parts
Fan speed control system components are:
1) Auto amp.
2) Fan control amp.
3) A/C LAN system (PBR built in mode door motor and air mix door motor)
4) In-vehicle sensor
5) Ambient sensor
6) Sunload sensor
7) Intake sensor
System operation
Automatic mode
In the automatic mode, the blower motor speed is calculated by the automatic ampli®er 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 ampli®er supplies a gate voltage to the fan
control ampli®er. Based on this voltage, the fan control ampli®er controls the voltage supplied to the blower
motor.
Starting fan speed control
Start up from ``COLD SOAK'' condition (Automatic mode)
In a cold start up condition where the engine coolant temperature is below 50ÉC, the blower will not operate
for a short period of time (up to 150 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 150 seconds as described above.
After this delay, the blower will operate at low speed until the engine coolant temperature rises above 55ÉC,
at which time the blower speed will increase to the objective speed.
Start up from normal or ``HOT SOAK'' condition (Automatic mode)
The blower will begin operation momentarily after the AUTO button is pushed. The blower speed will gradu-
ally rise to the objective speed over a time period of 3 seconds or less (actual time depends on the objective
blower speed).
SHA006FB
TROUBLE DIAGNOSESAUTO
Blower Motor (Cont'd)
HA-87
