Functional Description

Functional Description

The electromagnetic joint that operates the compressor Q11 is controlled by relay Q22 next to the relays and fuses of the injection/ignition system.

The coil of relay Q22 receives the key-operated supply (line protected by fuse F17 of G1 (box "A") or fuse F15 (box "C"); conversely the power line is supplied by battery current via wander fuse G65.

Relay Q22 is energised, and consequently supplies to 12V current to the electromagnetic joint Q11, according to the following logic managed by the M2.10.4 injection - ignition control unit, which is connected with the air conditioning system through:

• pin 40 which receives the request signal to turn the system on from the air conditioning system;
• pin 32 from which a "low" (earth) signal leads which controls the relay Q22 for engaging the 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.