JLG 450A Service And Maintenance Manual page 96

SECTION 3 - TROUBLESHOOTING
TROUBLE
Motor turns slowly in the direction of the last com-
mand.
Motor turns slowly at maximum command.
Poor response, function shuts off slowly
when command is removed.
No response to steer control.
3-12
Table 3-4.Chassis Assembly - Troubleshooting
PROBABLE CAUSE
Valve not returning to neutral.
Function speed switch malfunction.
Sticking spool due to contamination.
Valve spool is not traveling far enough due to:
Worn, leaking drive motor(s).
Engine RPM's set too low.
Low control pressure supply.
Function speed switch malfunction.
Amperage too low on controller.
Defective pump, low oil volume.
Low spool spring preload.
Sticking spool due to contamination.
Ramp set too high in controller.
Sticking control handle.
STEERING SYSTEM.
Circuit breaker open.
Hydraulic system oil low.
Hydraulic system pressure too low.
Damaged wiring on control switch or solenoid
valve.
Control switch not functioning properly.
Restricted or broken hydraulic line on valve
bank, hydraulic pump or rotary coupling. (If
equipped.)
– JLG Lift –
REMEDY
Check neutral springs.
Replace function switch.
Remove end cap and check spool freedom.
Repair as necessary.
Repair or replace drive motor(s).
Repair or replace drive motor(s).
Properly adjust engine RPM's.
Replace pressure regulator if necessary.
Replace switch.
Correctly adjust controller.
Repair or replace pump.
Check for correct spring and shims in end caps.
Remove end cap and check spool freedom.
Adjust controller.
Repair or replace controller.
Determine and correct cause; reset circuit
breaker.
Replenish oil as necessary.
Adjust pressure.
See proper wiring diagram.
Replace switch.
Clean, repair or replace line.
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