Case 580SR Service Manual page 1014

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Solenoid valve operation
Crab/4WS > 2WS
When the rear axle sensor detects alignment of its
axis, the control unit de-energizes the active steer-
ing solenoid valves and activates the solenoid
valves for 2WS.
2WS > Crab/4WS
When the rear axle sensor detects bridge align-
ment, all the solenoid valves for 2WS are de-activat-
ed and the solenoid valves for the selected mode
are energized.
Crab > 4WS and 4WS > Crab
When the rear axle sensor detects alignment the
2WS temporarily activates (energizing the corre-
sponding solenoid valves) until, after overcoming
the condition of rear bridge alignment, the desired
steering type activates when, by reversing the steer-
ing swing direction, the rear axle sensor detects
alignment.
Solenoid valve failure
The operation condition of any solenoid valve output
is tested each time the selected steering requires its
supply. Even when only one solenoid valve output is
short circuited or open, the control unit provides to
cut the supply to all the solenoid valves by means of
the self protection (the control unit is locked) and to
signal this condition (short - or open - circuit) by
means of the three warning lights relative to steering
flashing at the same time. Once the solenoid valve
causing the failure has been de-energized or the
correct operation has been reset.
Buzzer operation
Buzzer operation depends on setting of pin 2 of the
12 way connector:
Z Pin 2 not connected (North America only). If 12 km/
h is exceeded in crab mode, the buzzer sounds.
Z Pin 2 grounded (Outside of N/America). If 12 km/h
is exceeded in crab or 4WS mode, the buzzer
sounds.
Buzzer operation is intermittent, 250 ms on and 250
ms off.
The control unit is set at 9 km/h; steering mode
change is not possible when this speed is exceed-
ed.
Solenoid valve output
Solenoid 2WS
EVA2
EVA3
EVB2
EVB3
SECTION 55 - ELECTRICAL SYSTEM
4WS CRAB
X
X X
X X
X
Speed pulses
Speed pulses are drawn from EGS-CLARK control
unit. Output reference values of clark transmission
are:
Z 7 Hz for 1 km Æ
Z 14 Hz for 2 km Æ
Z 35 Hz for 5 km Æ
values in V -8 and +8.
The speed calculation has been determined with a
tyre having a circumference of 4.165 m.
Steering type storage
The steering type is stored in a non-volatile memory
each time the machine is turned off. This information
is therefore stored for an indefinite time even with
the supply cut off.
Start-up and axle recovery
The control units are supplied with a storage of the
last steering selected at two wheels. With this steer-
ing type selected, it is always possible to recover the
axle alignment; "short-circuit" the sensor or front and
rear axles, supply the machine (with the switch in 2
wheel position) and select the type of 4WS enabling
the bridge alignment.
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