General description

GENERAL DESCRIPTION

The system with thermostatic adjustment controls the climate control system semi-automatically:

In fact it automatically controls the following - on the basis of the temperature required in the passenger compartment - :

• air temperature at the vents
• fan speed (continuously changing);

On manual intervention it controls:

• fixed fan speed (4th speed)
• compressor engagement (air cooling circuit)
• air recirculation engagement
• "fast defrosting" function

The distribution of the air flow to the various vents is adjusted completely by hand (through bowden cables).

Operating logic

A special electronic control unit manages automatic operation of the system controlling the thermodynamic parameters in order to provide the climatic comfort (temperature and humidity) required by the occupants of the vehicle.

According to the requests received and the temperature conditions detected, the control unit sets certain functions to adapt the temperature of the passenger compartment to the one required (for further details see Group 50).

Controls:

• The left knob (1) selects the temperature required: it is connected to a potentiometer which detects the various angular positions and transmits a signal to the electronic control unit for a total of 15 different positions (one step corresponds to one degree centigrade); the two extreme positions "LO" and "HI" correspond to the request respectively for the coldest and warmest level.
• The centre knob (2) adjusts air ventilation: this too, is connected to a potentiometer which detects the different angular positions and transmits a signal to the electronic control unit. There are four possible types of air flow with fixed manual settings (1, 2, 3 and 4), while in the "AUTO" position, the system itself automatically selects the most suitable flow rate for reaching or keeping the required temperature.
• NOTE: Position "0" indicates minimum ventilation: the fan is off and only a light flow of dynamic air will go through the vents. With the compressor engaged, the fan is always "forced at first speed, also with the knob at "0".
• The right knob (3) selects air flow distribution to the passenger compartment which can take place in five different ways: this selection takes place manually through a cable that controls the movement of the distribution ports.
• When the distributor knob is turned completely clockwise it activates - through a special microswitch - the "fast defrosting" function - yellow serigraph "A" - fast defrosting involves:
• maximum air flow rate
• mixing with the highest amount of warm air available
• dynamic air, regardless of the position of the button (5)
• compressor enabled, regardless of the position of the button (4)
• When button (4) is pressed it enables operation of the compressor (air cooling circuit); when the button is released it cuts off the compressor. Engagement is fully manual: only in the "fast defrosting" mode is the compressor still enabled also when the button is released.
• Actual compressor engagement however, also depends on other conditions:
• outside temperature below 5°C: (disengagement below 4°C and re-engagement above 6°C)
• temperature detected by the antifrost sensor: (disengagement below 3.5°C, re-engagement above 5°C).
• The compressor may also be disengaged by the 4 level pressure switch or by the engine control unit. This logic depends on the different engine control units, as described in the specific "Engine Control" sections.
• When button (5) is pressed it engages the air recirculation function; when the button is released it allows "dynamic" air from outside into the passenger compartment.
• Engagement takes place only manually: recirculation is cut off even if the button is pressed only in the "fast defrosting" mode.