AIR CONDITIONING - Description

Description

The air conditioning system includes the heater and has the function of producing cold, dehumidified air by switching on the compressor and the refrigeration system.

The climate control system is operated through two control knobs in the dashboard (each knob carries out a dual function: one with an outer ring nut, one with a proper knob in the centre:

• the ring nut for the left knob mechanically controls the mixture flap between hot and cold air; the inner knob electrically controls the ventilation of the air at four different speeds;
• the ring nut for the right knob, mechanically operated via a cable, controls the opening of the flaps which regulate the distribution of air flows; the inner knob mechanically controls the engagement of the recirculation function.

The control panel also contains the button for engaging the air conditioning compressor See E6021 COMPRESSOR ENGAGEMENT.

For more details, Characteristic of working principle 5040 AIR CONDITIONING CASING AND COMPONENTS

There is also a red button in the control unit for switching on the hazard warning lights See E2020 DIRECTION INDICATORS / HAZARD WARNING LIGHTS and a button for switching on the heated rear windscreen See E3030 HEATED REAR WINDSCREEN AND DOOR MIRROR DEFROSTING.

The fan is supplied by a line protected by a special fuse and controlled by a special relay in the engine compartment control unit.

The operation of the fan at different speeds is achieved through a resistive divider, protected by a special thermal fuse to prevent overheating.

The control unit is supplied by a line controlled by the ignition and protected by a fuse in the underdashboard control unit.

Two-zone climate control system

Description

An automatic system manages the passenger compartment climate control, i.e. temperature and ventilation with recirculation and air flow orientation, with separate management of the temperature for the left and right hand sides of the passenger compartment.

A dedicated control unit manages system operation by controlling:

• air temperature at the driver/passenger vent;
• Air distribution to the vents.
• speed of the fan (varies continuously);
• activation of the compressor (air refrigeration circuit);
• activation of air recirculation;
• The MAX-DEF fast defrost function (i.e. a set of actions which allow both the windscreen and the rearscreen to be demisted quickly);

The control unit sets the above parameters in order to adjust passenger compartment temperature to the required level. The system controls are located outside the control unit housing.

The following parameters/functions can be modified manually:

• fan speed;
• distribution direction
• compressor disablement
• defrosting/demisting:
• recirculation.

Manual selections always take precedence over automatic selections and are stored until the user deliberately cancels the command, allowing the automatic device to take control over the relevant function.

The control unit downloads information on interior and exterior temperature and climatic conditions via special sensors.

• exterior temperature sensor, locate on the driver's side door mirror. The sensor reading is downloaded by a control unit on the door and filtered as necessary; it is then sent via the CAN network to the climate control system ECU (to instrument panel and other appliances).
• lower mixed air temperature sensor (right and left);
• upper mixed air sensors (right and left);
• sunlight sensor, which measures the sun's rays on the windscreen;
• exhaust gas presence sensor (A.Q.S.: Air Quality Sensor):supplies a signal when the air pollution index exceeds a preset level of harmfulness. This signal turns on the recirculation to prevent polluted air entering the passenger compartment;
• demisting sensor, which detects the presence of water droplets (mist) on the inner surface of the windscreen; this information turns on the relevant demisting strategy., which alters the air and ventilation distribution pattern.

After processing the information, it adjusts passenger compartment air intake speed by means of the fan motor and air temperature by means of two mixer actuators (one for the right side and one for the left). It also controls flow distribution via another actuator and - lastly - the interior/exterior air recirculation function via a final actuator.

When required, the ECU automatically activates the cooling circuit and dehumidifies the air by operating the air conditioner compressor See E6021 COMPRESSOR ENGAGEMENT.

For more details, Characteristic of working principle 5040 AIR CONDITIONING CASING AND COMPONENTS.

The climate control system ECU receives a signal from the body computer to indicate that the windscreen washer is on and activates the recirculation function to prevent the liquid detergent smell from entering the passenger compartment.

The vehicle speed signal - received by the CAN network - is used to filter outdoor temperature and adjust ventilation and the dynamic air intake according to car speed.

The body computer continually downloads a battery voltage signal for comparison with its limit value. If the recorded battery voltage is lower than the threshold, the computer cuts in via the CAN network to send a signal to disable a series of appliances: this includes the fan control.

The climate control system control unit is supplied by two lines, one direct and one controlled by the ignition, protected by fuses in the underdashboard control unit. the fan is supplied by a line protected by a special fuse and by a specific relay in the engine compartment control unit.