Relay T05 for engine compartment junction unit B001 controls the circuit for engaging the compressor.Relay coil T05 of B001 (pin 58 of connector B) is powered when the ignition is on (15/54), along the line protected by fuse 87 of B001.In versions with manual air conditioning the compressor engagement button, located in control unit H080, sends the compressor engagement request signal to Body Computer M001 (pin 49 of connector B) via electronic thermostat N086.However, in versions with automatic air conditioning, the air conditioning control unit M070 (pins 10 and 9 of connector A) sends this request signal via the B-CAN to Body Computer M001 (pins 57 and 58 of connector B).In both cases Body Computer M001 (pins 44 and 45 of connector B) sends the enabling signal via the C-CAN to engine management control unit M010 (pins 89 and 88 of connector A). See E1050 CAN CONNECTION LINES On the basis of internal control logic, control unit M010 (pin 11 of connector A) sends the compressor engagement command, exciting relay T05 of B001 (pin 59 of connector B): in this way the air conditioning compressor engagement solenoid L020 is powered with a 12 V voltage.If linear sensor K120 signals to control unit M010 (pin 57 of connector A) that the pressure value is too high or too low, then control unit M010 excludes the engagement of the compressor.Linear sensor K120 receives a power supply and reference earth at pins 28 and 7 respectively of connector A of engine management control unit M010.