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 junction unit B1 .Both are energized by an earth control signal coming from the engine management control unit M10.If the engine coolant reaches a first temperature level, control unit M10 sends a signal - from pin 13 of connector A - to energize the fan 1st speed relay T6, which then sends power to fan N11 via additional resistance O10: the fan turns at the first speed (slow).The engine temperature sensor K36 receives a reference earth from pin 29 of connector B of control unit M10, and sends a signal proportional to the engine coolant temperature to pin 43 of the same control unit.If the engine coolant reaches a first temperature level, control unit M10 sends a signal - from pin 12 of connector A - to energize the fan 2nd speed relay T7 which then sends power to fan N11 directly: the fan turns at the maximum speed.