Compressor engagement

COMPRESSOR ENGAGEMENT

(3.0 V6 24v engine)

The electromagnetic joint that operates the compressor Q11 is controlled by relays Q22 and Q32, located in the engine compartment, RH side.

The coil of relays Q22 and Q32 receive the key-operated supply (line protected by fuse F17 of G1); their power line is supplied with battery voltage through fuse Q39 (30A).

Relay Q22 is energised, consequently it supplies 12V current to the electromagnetic joint Q11, according to the following logic:

• relay Q32 is energised by an earth signal leading from Q69, which is in turn energised with a positive signal leading from the compressor engagement switch Q68; this signal crosses the control knob Q4 which cuts it off when the knob is at "OFF": in fact in this condition, the compressor cannot be engaged. The same signal simultaneously controls fan engagement at 1st speed ("Fan and Recirculation Control")

• relay Q32 consequently sends two signals to the Motronic control unit S11: a direct signal to "request compressor engagement" - pin 64 - and a second signal that crosses the minimum and maximum pressure switch (trinary) Q20 which cuts in in the event of high or low pressure in the cooling system: in this case the signal does not reach the control unit - pin 65 - which does not command the compressor

• The control unit "refers" the command signal - pin 48 - at relay Q22 which is energised and supplies the joint Q11 which thus engages the compressor, but only when the internal logic has checked determine conditions (e.g. the compressor is not engaged in the event of the need for full power at the engine, etc..)