JLG 450A Service And Maintenance Manual page 97

TROUBLE
Machine hard to steer or steering is erratic.
Steering inoperative.
Machine will not steer left or to the right.
3120869
Table 3-4.Chassis Assembly - Troubleshooting
PROBABLE CAUSE
If equipped, swivel coupling leaking internally.
(Seals defective.)
Steer control valve not functioning properly.
Steer cylinder not functioning properly.
Hydraulic system oil low.
Restricted hydraulic line or fitting.
Restricted crossover relief valve.
Steer system pressure low.
Bent linkage (tie rods).
Hydraulic pump not functioning properly.
Steer cylinder not functioning properly.
Damaged wiring on control switch or solenoid
valve.
Solenoid valve not functioning properly.
Control switch not functioning properly.
Relief valve improperly set or not functioning
properly.
Steer cylinder not functioning properly.
Wiring on control switch is damaged.
Wiring on solenoid valve damaged.
Coil in solenoid damaged.
No oil flow or pressure to steer circuit.
Bent cylinder rod.
Damaged tie rod.
Crossover relief valve sticking.
Cylinder packing defective.
– JLG Lift –
SECTION 3 - TROUBLESHOOTING
REMEDY
Repair or replace coupling.
Repair or replace valve.
Repair or replace cylinder.
Replenish oil as necessary.
Clean, repair or replace line or fitting.
Clean or replace valve.
Adjust pressure.
Repair or replace linkage as required.
Repair or replace pump.
Repair or replace cylinder.
See proper wiring diagram.
Repair or replace valve.
Replace switch.
Reset, repair or replace valves as required.
Repair or replace cylinder.
See proper wiring diagram.
Repair or replace wiring.
Replace coil.
Take pressure reading at steer valve and adjust
as necessary.
Repair or replace cylinder.
Replace tie rod.
Repair crossover relief valve.
Repair or replace cylinder.
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