The V5 Full Automatic Temperature Control (FATC) System
The full automatic temperature control (FATC) uses the integrated control panel
as the driver's interface to the system. The FATC receives driver's input signal and
various input signal from sensors and controls the actuators to maintain driver's
desired room temperature. Refer to Manual Control Heating, Ventilation,
and Air Conditioning System
for general information details for the following:
| • | System Components -- Functional |
| • | V5 Compressor -- Operation |
| • | V5 Compressor -- General Description |
System Components-Control
Controller
The operation of the A/C system is controlled by the switched on the control
head. This console-mounted controller consist of control knobs and a vacuum fluorescent
display (VFD) indicating the status of the control settings selected.
Temperature Control Switch
| • | Raise the temperature of the air entering the vehicle by pressing upper
part of the switch, with the red arrow pointing upward. |
| • | Lower the temperature of the air entering the vehicle by pressing lower
part of the switch, with the blue arrow pointing downward. |
| • | Actuate the air mix door by an electrical motor. |
| • | Varies the mix of the air passing through the heater core with the air
bypassing the core. |
| • | Each press of the switch changes the set temperature by increments of
0.5°C (1°F) this is shown in the temperature window on the function display. |
AUTO Switch
Maintains the set temperature automatically. In this mode, the full automatic
temperature control (FATC) system controls the following:
| • | The intake air door motor |
OFF Switch
Turns the automatic air conditioning and fan control off.
MODE Switch
Allows manual selection of the airflow direction.
| • | Selection is shown on the function display. |
| • | Each time the MODE switch is pressed, the next function is displayed. |
Intake Air Control Switch
Switches between fresh air intake, the default, and recirculating air. Airflow
arrows on the display indicate the mode in effect.
A/C Switch
Allows manual selection and control of the air conditioning function
Rear Window and Side Rear View Mirror Defroster Switch
Defrost rear window and side rear view mirror. When pressed, it operates for
8-12 minutes by the timer in the controller.
Defrost Switch
Cause the mode motor to direct all air to the windshield and aide window outlets
for maximum defrosting.
- Mode: Defroster
- Intake Air: Fresh
- A/C: ON (If the outside temperature is below than 1.5°C, the A/C would
not operate.)
Fan Control Switch
Allow manual selection among six-fan speeds.
Vacuum Fluorescent Display (VFD)
| • | Temperature setting -- indicates the temperature set with temperature
control knob. |
| • | Auto status -- Indicated whether the system is operating in the full
automatic mode or manual mode. |
| • | A/C -- A snowflake icon indicating whether the A/C is On or Off. |
| • | Intake Air -- Indicates whether the intake air is fresh (from outside)
or recirculating. |
| • | Mode -- Indicated by icon, the mode chosen by the system is shown
by illumination of arrow indicating the air path. |
| • | Defrost -- Indicates whether the defroster is ON of not. |
| • | Fan speed -- Indicates the fan speed by illuminating a bar based
segment from low to high speed by adding additional segments. |
Pressure Transducer
Pressure transducer switching incorporates the functions of the high-pressure
and the low-pressure cutout switches along with the fan cycling switch. The pressure
transducer is located in the high-side liquid refrigerant line between the right strut
and the air cleaner assembly. The output from this pressure traducer goes to the electronic
control module (ECM), which controls the compressor function based on the pressure
signal.
Sun Sensor
Sun sensor is a photo diode that detects lights. Resistance of the diode can
be measured as current by using voltmeter according to increasing sun loads. If the
sun sensor is error, no sun load will be substitute.
In-Car Sensor
In-car sensor located in left side of full automatic temperature control (FATC)
controller, is a sensor that detects the interior air temperature and a thermistor
that decreases its resistance when temperature up and increases when temperature down.
If there is open or short in the sensors, 25°C (77°F) will be substitute.
Ambient Sensor
Ambient sensor is a thermistor that decreases its resistance when temperature
up and increases when temperature down and it detects ambient air temperature. If
there is open or short in the sensors, 25°C (77°F) will be substitute. The
sensor is located in the left back side of front bumper.
Coolant Temperature Sensor
Coolant temperature sensor is a thermistor that decreases its resistance when
temperature up and increases when temperature down. It detects coolant temperature
to operate the blower speed at low when the coolant temperature is less than 50°C
(122°F). If the coolant temperature sensor is open or short, 100°C (212°F)
will be substitute.
Mode Control Motor
The mode control motor is located in heater/air distribution case assembly and
selects vents by the signal of the FATC.
Intake Air Control Motor
The Intake air control motor is located outside of evaporator case and changes
intake airflow recirculation or fresh by the signal of the FATC.
Air Mix Door Motor
The air mix door motor is located on left side of heater module. The air mix
door motor controls the exhaust air temperature by the signal of the FATC.
Specific Operation of V5 FATC
There are several specific operation modes in this fully automatic temperature
controller (FATC).
Max Cold Mode
When the temperature set at LO 18°C (64.4°F) the controller start max
cold mode and control air conditioning system as below.
| • | Intake Air: Recirculation |
Max Hot Mode
When the temperature set at HI 32°C (90°F) the controller start max
hot mode and control air conditioning system as below.
| • | Blower Speed: Auto High |
| • | Air Mix Door: Fully Open |
Wiper Related Operation
When operating the wiper, the controller turns A/C ON and changes the intake
air mode to fresh with one minute time delay from first wiper operation if FATC is
operated in AUTO mode.
Wide-Open Throttle (WOT) Compressor Cutoff
During full-throttle acceleration, the throttle position (TP) sensor sends a
signal to the ECM, which then controls the compressor clutch.
High RPM Cutoff
As engine RPM approached the maximum limit, the ECM will disengage the compressor
clutch until the engine slows the a lower RPM.
