Functional Description

Functional Description

The electromagnetic joint which operates the compressor Q11 is controlled by relay Q22 located next to terminal strip G56 which contains the MAXI FUSES.

The coil of relay Q22 receives the key-operated supply (line protected by fuse F15 of fusebox G1; while the power line is supplied by battery voltage through wander fuse Q65.

Relay Q22 is energised and consequently supplies 12 V to the electromagnetic joint Q11, according to the following logic, controlled by the injection electronic control unit which is connected with the air conditioning system through:

• pin 20 of connector C, which receives the signal requesting engagement of the system from the air conditioning system circuit;
• pin 32 of connector D, from which a ©low® (earth) signal leads that controls relay Q22 for engaging the air conditioner compressor Q11.

A special logic enables this engagement, as follows:

• it adapts idle speed to compensate the increase in absorbed power due to compressor engagement;
• if the engine needs high power (high throttle opening speed), full load, or high engine temperature, it momentarily cuts off compressor engagement.

The positive signal leading from the compressor engagement switch Q68 crosses the control unit Q21 which comes into action in the following conditions:

• low outside temperature: (disengagement below 4°C and re-engagement above 6°C);
• low mixed air temperature (disengagement below 3.5°C and re-engagement above 5°C).

The same signal also crosses the pressure switch Q20 which cuts in if the pressure of the cooling system is too high or too low: in this case the signal does not reach the control unit which does not command compressor engagement.