199002836 - E5020 ENGINE COOLING - FUNCTIONAL DESCRIPTION (Automatic air conditioning, Manual air conditioning)

FUNCTIONAL DESCRIPTION

Relay T1 T2 and T20 of engine compartment control unit B1 manage the activation of three speed fan N11: the coil power lines are protected by fuses F12 and F13 , also in engine compartment control unit B1 .All three are energized by an earth control signal coming from the engine management control unit M10.If the engine coolant reaches the first temperature level or linear sensor K120 indicates to the control unit M10 pin 87 of connector A - that a certain pressure level has been reached, control unit M10 sends a signal from pin 7 of connector A that excites the fan 1st speed relay T1, which then sends power to fan N11, all passing via additional resistance O10 : the fan turns at the first speed (slow).The linear sensor K120 receives a power supply and reference earth from the engine management control unit M10, pin 10 and 37 of connector A.If the engine coolant reaches the first temperature level or linear sensor K120 indicates to the control unit M10 - that a certain pressure level has been reached, control unit M10 sends a signal from pin 30 of connector A that excites the fan 2nd speed relay T20, which then sends power to fan N11, half passing via additional resistance O10: the fan turns at the second speed.If the engine coolant temperature reaches an even 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 8 of connector A to fan 2nd speed relay T2, which then sends power to fan N11 directly: the fan turns at the maximum speed.