The relay T5 for the engine compartment junction unit B001 controls the circuit for engaging the compressor L020.The power supply for the relay arrives via the direct line for the battery protected by fuse F19 of the engine compartment junction unit.The power supply for the coil for the compressor control relay T5 arrives directly from the main injection relay T9. In this case too it is a direct battery supply. See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENTFor versions with manual air conditioning, the climate control system control unit M070 sends the enablement signal for the compressor from pin 16; on versions with an automatic climate control system this signal is sent from pin 7 of connector A.The engine management control unit M010 receives the engagement request signal at pin 54 of connector A.On the basis of its internal control logic the control unit M010 sends the command - from pin 29 of connector A - for the effective engagement of the compressor which, by means of an earth signal, energizes the relay T5: in this way the air conditioning compressor engagement solenoid L020 is operated at a voltage of 12V.On versions with automatic climate control, if the compressor is actually activated, this signal is sent via the CAN from the engine management control unit M010 - pins 83 and 84 of connector A - to the climate control system control unit M070 - pin 1 and 10 of connector A - for the climate control system management and display logics.The Body Computer M001 manages the gateway for communication between the C-CAN and B-CAN. See E1050 CAN CONNECTION LINESIf the linear sensor for the fans K120 signals to the control unit M10 - pin 13 of connector A - that the pressure value of the refrigerant fluid is too high or too low, then the control unit M010 excludes the engagement of the compressor.