Manitowoc NATIONAL CRANE 900A - ANTI-TWO BLOCK TROUBLE DIAGNOSIS - HYDRAULIC

5-1
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Check to ensure ATB
electrical system is working
properly. Refer to ATB
electrical diagnosis
Do all three functions fail to
shut down
ELECTRICALHYDRAULIC
Examine solenoid valve for
sticking spool due to corrosion,
burrs, contamination, etc.
Work with individual section
which fails to shut down
YES NO
Disconnect drain line from
outlet end of unloader valve
Operate function at low
engine RPM
Oil flow from open port in
unloader valve
Remove unloader and flush
to dislodge contamination
that is blocking orifice
Poppet is not shifting.
Remove unloader and flush
to dislodge contamination.
Inspect to see that poppet is
free to shift in housing
Reinstall, retest and replace
unloader if problem persists
Reconnect drain line to outlet
end of unloader valve
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NO YES
Reference Only