The relay T5 for the engine compartment junction unit B1 controls the compressor engagement circuitThe supply for the relay via the line for specific fuse F19 of the engine compartment junction unit B1.The power supply for the coil for relay T5 arrives from the main injection relay T9 and from the ignition-controlled line protected by fuse F18, both located in the engine compartment junction unit B1 See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT The climate control system control unit M70 sends the enablement signal for the engagement of the compressor to the engine management control unit M10, pin 54 of connector A.On the basis of its internal control logic, the control unit M10 sends the command - from pin 29 of connector A - to engage the compressor which energizes the relay T5 so that the air conditioning compressor engagement solenoid L20 is operated at a voltage of 12 V.If the linear sensor for the fans K120 signal to the control unit M10 - pin 13 of connector A - that the pressure value is too high or too low, then the control unit M10 excludes the engagement of the compressor.The linear sensor K120 receives a power supply and reference earth from the engine management control unit M10, pin 12 and 22 of connector A.