Air cooling system:

Air cooling system:

This is a closed loop system in which a fluid condenses and evaporates withdrawing heat from the air in the evaporator.

It mainly comprises:

• compressor, operated by the crankshaft through a belt: it is turned on and off through an electromagnetic joint controlled by the air conditioning system:

• Petrol version: the compressor is controlled by the electronic engine management system which adapts the idle speed when the compressor is engaged, or cuts it off under power absorption conditions which adversely affect the performance levels of the car;

• TD version: compressor engagement is controlled by a special control unit which takes account of a series of operating conditions of the system and of the engine, as described below.

NOTE: in both cases a variable displacement compressor is used: this configuration is made through a suitable adjustment valve and sloping plate which changes the inside geometry. This makes it possible to meet the different requirements of cold air without continuously energising and energising the electromagnetic joint: in fact the compressor will set itself to the maximum displacement position for high requirements and vice versa for low requirements.

• condenser, fitted in front of the engine coolant fluid radiator: when the car is stationary it stops the air needed for heat exchange, it is supplied operating the engine radiator fan;

• evaporator, exchanger that cools the air, located in the duct-distributor;

• accumulator/drier, which separates the fluid in liquid state from gas and also acts as a storage lung and filter for any foreign matter;

• four-level pressure switch (trinary): controls the safety and correct operation of the fluid circuit.

The 4 levels cut in at:

• 1st level = minimum pressure for compressor engagement.

• 2nd level = pressure requiring engagement of the first speed of the fans.

• 3rd level = pressure requiring engagement of the second speed of the fans (level not present in the previous 3-level pressure switches).

• 4th level = maximum pressure for compressor engagement.

compressor cut out thermal contact: - only TD version - : this cuts off the compressor if the engine temperature reaches dangerously high values (it is a contact on the thermostatic cup which opens the circuit above 111°C.

full load switch - only TD version - : this is a mechanical microswitch on the injection pump which, through the special compressor cut out control unit, cuts off the compressor, only temporarily, when the accelerator pedal is completely depressed (full load).

compressor cut out control unit - only TD version - : this momentarily disengages the cooling system under certain particular conditions in which the engine needs to deliver maximum power to the wheels, eliminating the power absorption of the compressor (e.g. when overtaking, fast acceleration, up hills, etc.).

The control unit brings about the following operating logic, or rather two different logics at low and high engine speed: below 2000 rpm as soon as the full load switch closes, the compressor electromagnetic joint is de- energised, and it is engaged as soon as the switch opens again; above 2000 rpm the supply cut off to the compressor only lasts 8 seconds, after which it is restored.

Engine fan control:

When the car is travelling at low speed, dynamic air cooling on the condenser lowers and it is necessary to engage the fan that cools the engine radiator and the condenser. This takes place through the 4-level pressure switch which prevents an increase of the pressure at the condenser: the engine fan is initially engaged at first speed (level of appr. 15 bar) then, at second speed (level of appr. 20 bar).

Fuses and relays:

The system fuses and relays are grouped as follows:

• next to the fusebox G1: 30A fuse G255 (only G1, B), 10A fuse Q65, relay I78 (only G1, B), relay I99 (only G1, B), relay Q22 (only TD);

• in the "maxi fuse" box G56: 50A fuse G254;

• on the fan duct: relay I100 (only TD);

• next to the i.e. fuses and relays i.e. (only petrol version): relays Q22 and I100;

For further details concerning this system, refer to Group 50 "CLIMATE CONTROL".