TM 9-4940-568-342-64 Table 2-7. Crane Troubleshooting (CONT).MALFUNCTIONTEST OR INSPECTIONCORRECTIVE ACTION10. BOOM DOES NOT RAISE OR LOWER.WARNINGNever disconnect any hydraulic hose or part while FRS is run-ning. Allow several minutes for pressure to relieve itself. WithFRS, operate control valves fully in each direction to relievetrapped pressure.Before testing hydraulic system with a flow meter, always openthe pressure control valve all the way by turning the knobcounter clockwise to DECREASE. Failure to do so may causehydraulic lines to burst, causing personal injury.When increasing hydraulic system pressure with the pressurecontrol valve, always increase pressure slowly. If pressure is in-creased too fast, damage to hydraulic system or test set will re-sult.CAUTIONChecking system pressure involves putting valves into relief. Relief is defined as apoint when a needed system pressure is reached, causing excessive pressurizedhydraulic fluid to be directed to the hydraulic reservoir.Relief is accomplished either by operating the system in a manner which will createrelief or by using the loading valve on the flow meter, which will simulate theoperating conditions. Putting valves into relief should be limited to no more than 10seconds to prevent excessive heat buildup.NOTEUnless called for in the test being done, all pressure tests will be done with FRS 24V MASTER switch in the ON position, and hydraulic oil temperature at 130-150F(54-66 C).Unless advised otherwise, the FRS 24V MASTER switch and the crane MAINPOWER switch must be in the ON position for all voltage checks.Before performing troubleshooting procedures, make sure there are no restrictionsin pressure or return lines.If a boom lift cylinder must be isolated, connect flow meter at cylinder and discon-nect line between cylinders.If boom does not lower, go to Test 2.
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