The relay J30, located on the fan duct, manages the engagement of the fans N11 and N12 at the first speed: the coil and the power line are supplied by the line protected by fuse F6 of the engine compartment junction unit B1.If the engine coolant reaches an initial temperature level, or the linear sensor K120 signals to the control unit M10 - pin 13 of connector A - that a certain pressure level has been reached, then the control unit M10 sends a signal - from pin 90 of connector A - which energizes the relay J30, which sends the power supply to the fans N11 and N12 via the additional resistances O10 and O12: the two fans turn together at the first speed (slow).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.Relays T6 and T7 of the engine compartment junction unit B1 manage the switching on of the two speed fan N11: the coil power lines are protected by fuses F6 and F7 , also in engine compartment control unit B1 .If the engine coolant reaches a higher temperature level, or the linear sensor K120 signals to the control unit M10 - pin 13 of connector A - that a higher pressure level has been reached, then the control unit M10 sends a signal - from pin 69 of connector A - which energizes the two relays T6 and T7 which send the power supply directly to the fans N11 and N12 which turn together at the maximum speed.