Manitowoc National Crane 800D User Manual

National Crane Published 5-27-2018 Control # 039-06 5-31
800D SERVICE
Anti-two Block Trouble Diagnosis — Hydraulic
Note: None of the internal parts of the unloader valves are serviceable.
Anti-Two Blocking System fails to
shut down hoist up, boom down
and boom extend
Do all three functions fail to
shut down
Remove unloader and flush
to dislodge contamination
that is blocking orifice
Check to ensure ATB
electrical system is working
properly. Refer to ATB
electrical diagnosis
Work with individual section
which fails to shut down
Examine solenoid valve for
sticking spool due to corrosion,
burrs, contamination, etc.
HYDRAULIC
ELECTRICAL
NO
YES
Disconnect drain line from
outlet end of unloader valve
Operate function at low
engine RPM
Oil flow from open port in
unloader valve
YES
NO
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 uploader valve
9388
Fo
r
Reference
Only

Manitowoc National Crane 800D Specifications

General

Brand	Manitowoc
Model	National Crane 800D
Category	Construction Equipment
Language	English