TM 9-4940-568-20
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Table 2-21. Crane Troubleshooting (CONT).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
5. BOOM DOES NOT LOWER WITH REMOTE CONTROL.
NOTE
Before performing crane troubleshooting procedures, make sure the FRS electrical
supply system is functioning properly. Insure that Overload Shutdown System (OSS)
is functioning properly and lockouts are not engaged.
Unless advised otherwise, the FRS 24V MASTER switch and the crane MAIN
POWER switch must be in the ON position for all voltage checks.
Test 1.
Are the boom up, hoist up, and telescope out functions also not working using
remote control?
If none of the above listed functions operate, go to Test 2.
If boom up, hoist up, and telescope out function properly, go to Test 3.
Test 2.
Are the boom up, hoist up, and telescope out functions also not working using
manual control?
If none of the above listed functions operate, faulty overload shutdown system,
Notify Supervisor.
If boom up, hoist up, and telescope out function properly, faulty lockout solenoid
valve, Notify Supervisor.
Test 3.
Loosen screw and remove connector from boom DOWN solenoid. Place
EMERGENCY STOP switch in ON position. Hold remote control unit boom
controller in DOWN position and check for 24 volts between solenoid connector,
terminal 1, and known good ground.
If 24 volts are present, go to Test 4.
If 24 volts are not present, turn MAIN POWER switch OFF and go to Test 10.
Test 4.
Disconnect the remote control cable from the remote control unit and remote control
hook-up connector on crane sub-frame. Check the cable for continuity between the
two cable ends, terminal M.
If no continuity is found on terminal M, replace the remote control cable.
If continuity is found, go to Test 5.
