Functional Description

Functional Description

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

The coil of relay Q22 receives the key-operated supply (line protected by fuse F17 of G1 (box “A” and “B”) or by fuse F15 box “C”; conversely the power line is supplied by battery current through wander fuse Q65.

The relay Q22 is energised, thus it supplies 12V current to the electromagnetic joint Q11, according to the following logic, managed by the injection - ignition control unit, which is connected with the air conditioning system through:

• pin 40 (M2.10.4) or pin A31 (M1.5.5) which receives the request signal for engaging the system from the air conditioning system circuit;

• pin 32 (M2.10.4) or pin A19 (M1.5.5) from which a Elow^a signal (earth) leads that controls relay Q22 for engaging the conditioner compressor Q11.

A special logic enables this engagement. In particular:

• it adapts idle speed to compensate the increased power absorption caused by engaging the compressor;
• if the engine needs power (high throttle opening speed), full load, or high engine temperature, it momentarily stops engaging the compressor.

The positive signal leading from the compressor engagement switch Q68 crosses the antifrost thermostat Q71 which cuts in if the temperature is too low and the pressure switch Q20 which cuts in if the cooling system pressure is too high or too low: in this case the signal does not reach the control unit and it does not command engagement of the compressor.