Anti-Two Blocking System
fails to shut down, hoist up
and boom extend
Check for voltage across
leads of limit switch with
weight supported
Check limit switch or actuator
arm for sticking - Repair or
replace switch
Fuse blown
Test HCA & ATB relays for
proper operation (see
Schematic)
Examine solenoid valve for
sticking spool due to corrosion,
burrs, contamination, etc.
Replace relay
Replace fuse
YES
NO
NO
YES
NORMAL
RELAY OPERATION
FAULTY
RELAY OPERATION
9386
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