JLG G12-55A Service Manual - Manual (Page 65)

3-31 G10-55A, G12-55A
Boom
5. Drooping chain, or jerky
boom extend or retract
functions.
1. Chain(s) tension not properly
adjusted.
1. Adjust chain(s).
2. Chain(s) stretched or binding. 2. Replace chains as needed.
Refer to Section 3.7, “Boom
Section Separation
Adjustment.”
3. Wear pads loose, contaminated,
excessively worn or damaged.
3. Replace wear pad. Refer to
Section 3.11, “Boom Wear
Pads.”
4. Contaminated, corroded or
rusted wear pad sliding
surfaces.
4. Remove contamination and/or
corrosion from wear pad sliding
surfaces and lubricate. If the
surfaces cannot be reconditioned,
replace the boom section(s).
5. Extend/Retract hydraulic system
not operating properly.
5. Refer to Section 8.4, “Hydraulic
Circuits.”
6. Damaged boom section. 6. Replace the damaged boom
section. Refer to Section 3.3,
“Boom Assembly Maintenance.”
6. Boom will not raise or lower. 1. Broken hydraulic hoses or tubes
and/or connection leaks.
1. Locate break, replace hose(s)
or tube(s), tighten connections.
2. Lift/lower hydraulic system not
operating properly.
2. Refer to Section 8.4, “Hydraulic
Circuits.”
3. Faulty lift/lower cylinder. 3. Repair cylinder. Refer toSection
8.8, “Hydraulic Cylinders.”
4. Seized boom pivot pin bearing. 4. Replace bearing.
7. Excessive Lift/Lower cylinder
pivot pin noise and/or wear.
1. Insufficient lubrication. 1. Lubricate at regular intervals.
Refer to Section 2.5, “Service
and Maintenance Schedules.”
Replace worn pins as needed.
Refer to Section 8.8, “Hydraulic
Cylinders.”
2. Worn self-aligning bushing(s). 2. Replace bushing(s) and
lubricate at regular intervals.
Refer to Section 2.6,
“Lubrication Schedules.”
Problem Cause Remedy