JLG 450A Service And Maintenance Manual page 90

SECTION 3 - TROUBLESHOOTING
TROUBLE
Boom extends and retracts erratically.
No response to swing control.
Boom will swing in one direction only.
3-6
Table 3-2.Boom Assembly - Troubleshooting
PROBABLE CAUSE
Hydraulic system oil low.
Wear pads worn.
Restricted or broken hydraulic line or fitting.
Control valve not functioning properly.
Worn seals in telescope cylinder.
Cylinder not functioning properly.
Counterbalance valve not functioning properly.
BOOM SWING SYSTEM
Swing function not activated within 7 seconds
after footswitch was depressed.
Hydraulic system oil low.
Swing control switch not functioning.
Restricted or broken supply line on valve bank or
hydraulic pump.
Control valve not functioning properly.
Swing motor not functioning properly.
Restrictor valve(s) plugged.
Foreign objects(s) wedged between swing
motor pinion and swing gear.
Pressure reducing valve in swing circuit malfunc-
tioning.
No electric power to valve.
Restricted or broken hydraulic line or fitting.
Control valve not functioning properly.
Foreign object(s) wedged between swing motor
pinion and swing gear.
Swing control switch not functioning properly.
– JLG Lift –
REMEDY
Replenish oil as necessary.
Replace pads as required.
Clean, repair, or replace line or fitting.
Repair or replace valve.
Replace seals.
Repair or replace cylinder.
Replace counterbalance valve.
Recycle footswitch.
Replenish oil as necessary.
Repair or replace swing control switch.
Clean or replace line.
Repair or replace valve.
Repair or replace motor.
Clean or replace restrictor valve.
Remove objects, check for damage, and repair
or replace component(s) as required.
Repair or replace pressure reducing valve.
See proper wiring diagram.
Clean, repair, or replace line or fitting.
Repair or replace valve.
Remove object(s), check for damage and repair
or replace component(s) as required.
Repair or replace swing control switch.
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