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
.
If the engine coolant reaches a first temperature
level, or the 4-stage pressure switch
K10 indicates to the control
unit M10 - pin 42 of connector A - that a first pressure level has been
reached, the control unit M10 sends a signal - from pin 90 of connector
A - to the fan 1st speed relay, which then sends the supply to the
fan N11 via the additional resistor O10: the fan thus turns at the
first speed (slow).
If the coolant reaches a higher temperature
level, or the 4-stage pressure switch
K10 indicates to the control
unit M10 - pin 81 of connector A - that a higher pressure has been reached,
the control unit M10 sends a signal - from pin 69 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.