The system is managed by the engine management control unit M010 which controls the two relays T06 and T07 located in the engine compartment junction unit B001.The engine management control unit acquires information relating to the temperature of the engine coolant from sensor K036.Engine coolant sensor/sender unit K036 receives a reference earth from pin 29 of connector A of engine control unit M010 and sends a signal proportional to engine coolant temperature to pin 54 of the control unit.The fan N011 motor receives a power supply at pin 1. This power supply can come from the line managed by relay T07 and protected by fuse F07 for the high rotation speed or from the line for relay T06 protected by fuse F06 for the regulation resistance O011 with a consequent decrease in the voltage at N011 to produce a lower rotation speed.A control signal is sent for relay T06 from pin 7 of connector B of M010 to pin 28 of connector C of B001. The control signal for T07 is sent from pin 8 of connector B of M010 and reaches pin 21 of connector C of B001.The regulation resistance O010 has the unique task of producing a drop in power at the supply line for N011 to allow the fan to operate at a lower speed. Resistance O010 receives a power supply from pin C of connector E of B001, whilst, when operating at the maximum speed, N011 takes a power supply directly from pin A of connector E of B001.Pin 2 of the fan N011 is earthed via the contact board at the negative pole of the battery A001 (connector F).