JLG 120HX Service Manual - Manual (Page 91)

SECTION 3 - TROUBLESHOOTING
3120819 – JLG Lift – 3-5
MAIN TELESCOPE SYSTEM.
No response to telescope control.
Telescope function not activated within 7 sec-
onds after footswitch was depressed. Recycle footswitch.
Telescope control switch inoperative. Repair or replace control switch.
Hydraulic system oil low. Replenish oil as necessary.
Damaged wiring on control switch or solenoid
valve. Repair or replace wiring.
Control valve not functioning properly. Repair or replace valve.
Restricted or broken supply line on valve bank or
hydraulic pump. Clean or replace line.
Telescope cylinder not functioning properly. Repair or replace cylinder.
Hydraulic pump not functioning properly. Repair or replace pump.
Boom will not extend.
Telescope function not activated within 7 sec-
onds after footswitch was depressed. Recycle footswitch.
Control valve not functioning properly. Repair or replace control valve.
Restricted or broken hydraulic line or fitting. Clean, repair, or replace line or fitting.
Pressure setting incorrect. Check pressure/re-adjust as necessary.
Telescope cylinder not functioning properly. Repair or replace cylinder.
Boom extends and retracts erratically.
Hydraulic system oil low. Replenish oil as necessary.
Wear pads worn. Replace pads as required.
Restricted or broken hydraulic line or fitting. Clean, repair, or replace line or fitting.
Control valve not functioning properly. Repair or replace valve.
Worn seals in telescope cylinder. Replace seals.
Cylinder not functioning properly. Repair or replace cylinder.
Counterbalance valve not functioning properly. Replace counterbalance valve.
Fly section inoperative.
Broken drive chain. Repair or replace chain.
Broken drive sprocket or bent sprocket shaft. Replace shaft assembly.
Fly section extends and retracts erratically.
Drive chain out of adjustment. Adjust chain as required.
Table 3-2.Boom Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY