Functional Description

Functional Description

The electromagnetic joint which operates the compressor Q11 is controlled by relays Q22 e Q32.

Relays Q22 and Q32, have the coil supplied by the "key-operated" line (protected by fuse F17 of G1); the power line is supplied by battery voltage via fuse Q65 (10A) and the general fuse G384 (50A).

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

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

• relay Q32 consequently sends two signals to the Motronic control unit S11,: a direct signal to "request engagement of the compressor" to pin 41, and a second signal which crosses the minimum pressure switch (antifrost) Q9 and the minimum and maximum pressure switch (trinary) Q20 which cut in if the pressure in the cooling system is too high or too low: in this case the signal does not reach the control unit at pin 40, and the compressor is not engaged

• the control unit "relays" the control signal - pin 32 of S11 - to relay Q22 which is energised and supplies connector Q11 which 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..)