JLG 120HX ANSI Service Manual - Manual (Page 91)

SECTION 3 - TROUBLESHOOTING
3120686 – JLG Lift – 3-9
Counterbalance valve on tower lift cylinder
improperly adjusted or not functioning properly. Replace counterbalance valve.
Control valve not functioning properly. Repair or replace valve.
Worn seals in tower lift cylinder. Replace seals.
Upright level cylinder not functioning properly. Repair or replace cylinder.
Air in upright cylinder. Fully cycle upright level cylinder 2-3 times.
Holding valves on tower lift or upright level cylin-
der contaminated. Determine and remedy source of contamination.
Replace holding valve.
Relief valve set too low on level circuit. Correctly adjust valve.
Tower level master cylinder defective or leaking. Repair or replace master cylinder.
Air in tower master cylinder. Fully cycle tower master cylinder 2-3 times.
Seals worn or leaking in tower master cylinder. Repair master cylinder.
Table 3-2.Boom Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY