Manitowoc National Crane 800D - Page 136

SERVICE 800D
5-30
Published 5-27-2018 Control # 039-06
Anti-two Block Trouble Diagnosis – Electrical (Continued)
Anti-Two Blocking System shuts
down crane functions when
weight is freely suspended
12 volts at limit switch
Continuity check
lead wires
Fuse blown
Test HCA & ATB relays for
proper operation (see
Schematic)
Limit switch contacts closed
with weight suspended
Replace relay
Replace fuse
YES
NO
NO
YES
NORMAL
RELAY OPERATION
FAULTY
RELAY OPERATION
YES
NO
YES
NO
NO
YES
FAULTY
RELAY OPERATION
NORMAL
RELAY OPERATION
Test HCA & ATB relays for
proper operation (see
Schematic)
Continuity check lead
wires
Replace relay
Check for 12 volts at
solenoid valve
Replace limit switch or
check actuator arm for
free movement
Check continuity
across solenoid valve
Replace solenoid
Check valve for sticking
spool - Clean or replace
9387
Fo
r
Reference
Only