OPERATOR'S MANUAL MAINTENANCE

Section C - Electrics
Basic System Operation
Auto Boost Pressure
C-27 C-27
9803/9880-3
Auto Boost Pressure
Operation
C049920-1
Fig 30.
The auto pressure boost function is only available when
the excavator is in auto mode. By default it is not available
in precision and economy mode and is permanently on
(although not indicated on the EMS) in lifting mode.
In auto mode, when the boost pressure switch is closed the
2 stage relief valve, ECU1 o/p 24 (C-27) is energised
(according to the logic diagram,
K
Fig 31. ( T C-28)). This
allows a pressure increase in the excavating hydraulic
circuit thus generating extra digging force.
If the boost pressure switch is seen for less than 1.5
seconds then the 2 stage relief valve is energised until the
boost pressure switch is de-energised, then the logic
sequence is reset and will allow the sequence to be started
over again.
If the boost pressure switch is seen for more than 1.5
seconds then the 2 stage relief valve should stay open for
a further 1.5 seconds. The valve cannot be re-energised
for 9 seconds after the end of the last activation
However during travel operation (denoted by the travel
pilot switch input) the 2 stage relief valve is energised. If
the boost pressure switch is closed when the travel
pressure switch is valid, the solenoid will remain energised