38 MECHANICAL LIFTING GEAR
Manual lifting:
When switch C704 (lifting gear switch) is
operated (connection between contacts 3 - 1),
a voltage is applied to connection point 1 of
B071 through fuse E062, wire 1221, contacts
3 - 1 of switch C704, wire 4550, contacts 3 - 4
of relay G381 and wire 5180. This valve is
energised. The voltage is applied to
connection point 85 of relay G052 at the same
time through D622, wire 4552, contacts 30 -
87a of relay G066 and wire 4557. This is
activated and closes contacts 1 - 2. A voltage
is now applied to connection point 1 of B073
through contacts 1 - 2 of relay G052 and wire
4554. The oil pump motor starts to run.
If the oil pressure becomes too high (>160
bar), E524 will close. Voltage is now applied
to connection point 85 of relay G066 through
contacts 1 - 2 of E524. This is energised and
it breaks the connection 30 - 87a. Voltage is
now applied to connection point 85 of relay
G066 from wire 4552 through contacts 30 - 87
of relay G066 and wire 4558. This remains
energised. At the same time the voltage
through relay G052 is lost. Contacts 1 - 2
open and the voltage on connection point 1 of
B073 is lost. The pump motor is no longer
driven and the oil pressure drops.
Manual lowering:
When switch C704 (lifting gear switch) is
operated (connection between contacts 3 - 7),
a voltage is applied to connection point S1 of
D503 through fuse E062, wire 1221, contacts
3 - 7 of switch C704 and wire 4551. A voltage
is applied to connection point 1 of B072
through connection point 87 of D503 and wire
4553. This valve is energised. The voltage is
applied to connection point 85 of relay G052
at the same time through D623, wire 4552,
contacts 30 - 87a of relay G066 and wire
4557. This is activated and closes contacts 1 -
2. A voltage is now applied to connection
point 1 of B073 through contacts 1 - 2 of relay
G052 and wire 4554. The oil pump motor
starts to run.
If the oil pressure becomes too high (>160
bar), E524 will close. Voltage is now applied
to connection point 85 of relay G066 through
contacts 1 - 2 of E524. This is energised and
breaks the connection 30 - 87a. Voltage is
now applied to connection point 85 of relay
G066 from wire 4552 through contacts 30 - 87
of relay G066 and wire 4558. This remains
energised. At the same time the voltage
through relay G052 is lost. Contacts 1 - 2
open and the voltage on connection point 1 of
B073 is lost. The pump motor is no longer
driven and the oil pressure drops.
Automatic axle load protection:
If the pressure on the driven axle is greater
than the legal maximum, sensor E584 is
activated. This puts sensor E507 in ’stand-by’
mode. If the acceptable axle load increases
further (> 10 ton), sensor E507 automatically
lowers the trailing axle.
If the axle has been lifted, F097 (proximity
switch for trailing axle lifting gear) ensures
that relay G380 is energised through wire
3661. A voltage is now applied through fuse
E062, wire 1221, contacts 3 - 5 of relay G380
to connection point 1 of E507. This is
activated.
The voltage is immediately transmitted to S2
on D503. The signal sent by the axle load
protection proximity switch (E507) to S2 must
be maintained for at least 10 seconds before
the lifting gear electronic unit (D503) will
activate the valve (B072) and the lifting-gear
pump motor (B073) to lower the trailing axle.
This is to prevent the legal maximum axle
load being exceeded.
If the dashboard switch is operated within this
2.5 minute period, the electronic unit will be
reset and another 2.5 minute period will start.
The lifting-gear motor relay (G052) will also be
activated, thus activating the lifting-gear pump
motor (B073). This takes place through D623,
relay G066 (connection between points 30
and 87a) to connection point 85 of relay
G052. When a pressure of 160 bar is
reached, the oil-pressure limit switch (E524)
switches the lifting-gear pump motor (B073)
off through relay (G066) and relay (G052).
The trailing axle cannot be lifted for a period
of 2.5 minutes as the valve (B072) remains
energised. This valve must be in the
non-energised position to lift the trailing axle.
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