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 52 of connector A - that a first
pressure level has been reached, the control unit
M10
sends
a signal - from pin 20 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 51 of connector A - that a higher
pressure has been reached, the control unit
M10
sends a
signal - from pin 19 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.