The relays
T6
and
T7
in
the engine compartment unit B1 manage the switching on of the fan
N11
at two speeds: their coils are supplied by the ignition-controlled
line (15/54), while the power lines are protected by the fuses F6
and F7, of the engine compartment unit
B1
.
Both are energized by a control signal -
earth - coming from the engine control unit
M10, pins 14 and
30 of connector A, respectively.
If the engine coolant reaches a first temperature
level, or the linear sensor
K120 indicates to the control unit
M10 - pin 54 of connector B - that a certain pressure level has
been reached, the control unit M10 sends a signal - from pin 14
of connector A which energizes the fan 1st speed relay T6, which
then sends the supply to the fan N11 via the additional resistor
O10: the fan thus turns at the first speed (slow).
Linear sensor
K120
receives a power
supply and reference earth from the engine management control unit
M10
,
pins 53 and 5 of connector A.
If the coolant reaches a higher temperature
level, or the linear sensor
K120 indicates to the control unit
M10 that a higher pressure has been reached, the control unit M10
sends a signal - from pin 30 of connector A - to the fan 2nd speed
relay T7, which sends the supply directly to the fan N11: the fan
then turns at the maximum speed.