Manitowoc NATIONAL CRANE 900A - Page 89

2-29
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The following step-by-step analysis will be helpful in isolating and correcting almost every service problem if fol-
lowed in a step-by-step systematic manner. Use this information with the Hydraulic Schematic and the Illustrated Parts
Catalog to identify parts and follow flow paths. Start at top box and work downward step by step – don’t try to start in the
middle or skip steps.
Boom Creeping Down
Control Valve Centered
Replace
Compensating
Pressure Switch
Control Valve in
Meter in Position
Control Valve in Down
Position Normal
Operation
Center Valve
Cap Sensing Line Between
Counterbalance Valve and
Compensating Pressure
Switch
Incorrect Counterbalance
Setting
Bad Counterbalance Valve
Leaking Cylinder Seals
Yes No
Yes No
Stops CreepStill Creeps
Reference Only