JLG 150HAX ANSI Service Manual - Manual (Page 133)

SECTION 6 - SCHEMATICS
3120679 – JLG Lift – 6-5
Boom raises and lowers erratically.
Hydraulic system oil low. Replenish oil as required.
Restricted or broken hydraulic line or fitting. Clean or replace line.
Lack of lubricant on cylinder shafts and/or boom
pivot. Lubricate as required. (Refer to Lubrication
Chart)
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.
Manual lowering valve not functioning properly. Repair or replace valve.
Worn seals in lift cylinder. Replace seals.
Holding valve on cylinder not
functioning properly. Repair or replace valve.
High engine does not operate below horizontal.
Damaged wiring on boom limit switch. Repair or replace wiring.
Damaged boom limit switch. Replace switch.
MAIN TELESCOPE SYSTEM.
No response to telescope control.
Circuit breaker open. Determine and correct cause. Reset circuit
breaker.
Hydraulic system oil low. Replenish oil as necessary.
Damaged wiring on control switch, solenoid
valve or proportional valve. Repair or replace wiring.
Control switch or valve not functioning properly. Replace switch or 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.
Table 6-2.Boom Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY