Functional description

Functional description

• from chassis no. 4065018

The electromagnetic joint which operates the compressor Q11 is controlled by relays Q22 and Q32, located on the auxiliary bracket for relays and fuses.

Relays Q22 and Q32, have the coil supplied from the ignition switch (line protected by fuse F17 of G1); conversely the power line is supplied by battery voltage via fuse Q65 (7.5A).

The relay Q22 is energised, and thus supplies 12 V current to the electromagnetic joint Q11, according to the following logic:

BOXER 1.7 16v version:

• the relay Q32 is energised by a signal leading from relay Q69, which is 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 is at "OFF": in this condition, in fact, the compressor can not be engaged. You are reminded that the same signal simultaneously controls engagement of the fan at first speed ("Fan and Recirculation control")
• the relay Q32 consequently sends two signals to the Motronic M2.10 control unit S11,: a direct signal to "request compressor engagement" at 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 in the event of high or low pressure in the cooling system: in this case the signal does not reach the control unit at pin 40, and this does not command engagement of the compressor

• the control unit "relays" the command signal - pin 32 of S11 - to relay Q22 which is energised and supplies the joint Q11 which thereby engages the compressor, but only when the internal logic has checked determine conditions (e.g. the compressor does not engage in the case of the need for full power at the engine, etc.)

BOXER 1.3 and BOXER 1.6 (ROCHESTER) version

• the relay Q32 is energised by a signal leading from relay Q69, which is 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 is at "OFF": in this condition, in fact, the compressor can not be engaged. You are reminded that this signal simultaneously controls engagement of the fan at 1st speed ("Fan and Recirculation control")
• the relay Q32 consequently sends a signal to the control unit S40, at pin 8 (IAW) or pin A8 (Rochester), which crosses the minimum pressure switch (antifrost) Q9 and the minimum and maximum pressure switch (trinary) Q20 which cut in if the event of high or low pressure in the cooling system: in this case the signal does not reach the control unit S40 and this does not engage the compressor
• the control unit "relays" the command signal - pin 24 (IAW) or pin A15 (Rochester) di S40 - to relay Q22 which is energised and supplies the joint Q11 which thereby engages the compressor, but only when the internal logic has checked determine conditions (e.g. the compressor is not engaged if the engine needs full power, etc.)