JLG 120HX ANSI Service Manual - Manual (Page 86)

SECTION 3 - TROUBLESHOOTING
3-4 – JLG Lift – 3120686
Fuse is blown out on control card. Replace fuse.
Control valve not functioning properly. Repair or replace valve.
Hydraulic Pump not functioning properly. Repair or replace pump.
Lift cylinder not functioning properly. Repair or replace cylinder
Boom will not raise.
Lift function not activated within 7 seconds after
footswitch was depressed. Recycle footswitch.
Load capacity exceeded (personnel or equip-
ment on platform). Reduce load.(Refer to capacity placard.)
Hydraulic system oil low. Replenish oil as necessary.
Electrical failure to valves. See proper wiring diagram.
Restricted or broken hydraulic line or fitting. Clean, repair, or replace line or fitting.
Control valve not functioning properly. Repair or replace valve.
Pressure relief valve not functioning properly. Re-adjust or replace valve.
Bypass valve (dump) not functioning. Repair or replace valve.
Lift cylinder not functioning properly. Repair or replace cylinder.
Binding lift cylinder or boom pivot pin. Repair or replace cylinder or pin.
Boom will not lower.
See: Boom will not raise.
Pressure relief valve not functioning properly. Re-adjust or replace valve.
Holding valve not functioning properly. Re-adjust or replace valve.
Boom raises and lowers erratically.
Hydraulic system oil low. Replenish oil as required.
Restricted or broken hydraulic line or fitting. Clean, repair, or replace line or fitting.
Counterbalance valve on lift cylinder improperly
adjusted or not functioning properly. Replace valve.
Control valve not functioning properly. Repair or replace valve.
Worn seals in lift cylinder. Replace seals.
Cylinder not functioning properly. Repair or replace cylinder.
Boom drifts down.
Worn seals in lift cylinder. Replace seals.
Table 3-2.Boom Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY