Relays T6 and T7 of engine compartment control unit B1 manage the activation of two speed fan N11: the coil power lines are proteted by fuses F6 and F7 , also in engine compartment control unit B1 .Both are energized by an earth signal coming from the engine management control unit M10, pin 14 and 30 of connector A respectively.If the engine coolant reaches the first temperature level or linear sensor K120 indicates to the control unit M10 pin 5 of connector A - that a certain pressure level has been reached, control unit M10 sends a signal from pin 55 of connector A that excites 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).Linear sensor K120 receives a power supply and reference earth from engine control unit M10 , pins 3 and 15 of connector A.If the engine coolant temperature reaches a higher level or linear sensor K120 indicates to control unit M10 that a higher pressure level has been reached, then control unit M10 sends a signal from pin 59 of connector A to fan 2nd speed relay T7, which then sends power to fan N11 directly: the fan turns at the maximum speed.