Relays T1 and T2 of engine compartment control unit B1 manage the activation of two speed fan N11: the coil power lines are protected by fuses F12 and F13 , also in engine compartment control 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 T1, which then sends power to fan N11 via additional resistance O10: the fan turns at the first speed (slow).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 T2, which then sends power to fan N11 directly: the fan turns at the maximum speed.