Manitowoc NATIONAL CRANE 900A - ANTI-TWO BLOCK TROUBLE DIAGNOSIS - ELECTRICAL (CONTINUED)

5-1
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YESNO
NORMAL
RELAY OPERATION
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4&$3)'%%
12 volts at limit switch
Limit switch contacts closed
with weight suspended
Replace limit switch or
check actuator arm for
free movement
Check for 12 volts at
solenoid valve
Test HCAS & ATB relays for
proper operation (see
Schematic)
Check continuity
across solenoid valve
Continuity check lead
wires
Replace relay
FAULTY
RELAY OPERATION
NO
Replace solenoid
Check valve for sticking
spool - Clean or replace
YESNO
YES
Fuse blown
Test HCAS & ATB relays for
proper operation (see
Schematic)
Replace fuse
Continuity check lead
wires
Replace relay
YESNO
NORMAL
RELAY OPERATION
FAULTY
RELAY OPERATION
YES NO
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Reference Only