JLG 120HX ANSI Service Manual - Manual (Page 87)

SECTION 3 - TROUBLESHOOTING
3120686 – JLG Lift – 3-5
Function Speed, Drive Speed and High
Engine does not operate below horizontal.
Damaged wiring on level limit switch. Repair or replace wiring.
Solenoid failure. Replace solenoid.
Tripped circuit breaker. Reset circuit breaker.
Damaged level limit switch. Replace switch, repair or replace holder.
Defective relay, main terminal box. Replace relay.
Defective platform switch. Replace switch.
LOWER LIFT FUNCTION.
If the boom assembly does not fully lower.
The Mid and Lower Booms are out of synchroni-
zation. Refer to synchronize procedure.
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.
Table 3-2.Boom Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY