5
CHANGES IN THE ELECTRICAL SYSTEM
Changes in the electrical system from chassis number 0E527418
5-20
13 GEARBOX AND GATE PROTECTION
RANGE-CHANGE PROTECTION, GEARBOX
(gears 1 -> 5)
This shift-down safety prevents shifting down
into the lower range (gears 1, 2, 3 and 4) once
the vehicle speed has exceeded approx. 30
km/h. The shift-down safety is installed on
vehicles with single H-type gearing.
In the case of an electrical malfunction (voltage
drop out), the safety is activated and the gears
1, 2, 3 and 4 cannot be re-engaged.
OPERATION
If the vehicle speed is lower than 30 km/h (this
value depends on the engine type and gearbox
model), connection point 51 will be earthed in
the unit. Voltage is now applied to connection
point 85 of relay G420 through fuse E019 and
wire 1202. Connection point 86 is earthed via
connection point 51 of the CTE unit (D884).
Relay G420 is energised (points 30 and 87 are
connected). A voltage is now applied to
connection point 2 of valve B079 (Valve,
single-H protection) through fuse E019 and wire
1202). Connection point 1 of valve B079 is
connected to connection point 30 of relay G420
through wire 4030. If the contacts of relay G420
are closed (points 30 and 87 are connected),
valve B079 will be activated. Now it is possible
to shift down.
If the vehicle speed exceeds 30 km/h, the CTE-3
unit will break the earth connection and shifting
down is no longer possible.
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