JLG 120HX ANSI Service Manual - Manual (Page 96)

SECTION 3 - TROUBLESHOOTING
3-14 – JLG Lift – 3120686
Motor turns slowly in the direction of the last com-
mand.
Valve not returning to neutral. Check neutral springs.
Function speed switch malfunction. Replace function switch.
Sticking spool due to contamination. Remove end cap and check spool freedom.
Repair as necessary.
Motor turns slowly at maximum command.
Valve spool is not traveling far enough due to: Repair or replace drive motor(s).
Worn, leaking drive motor(s). Repair or replace drive motor(s).
Engine RPM’s set too low. Properly adjust engine RPM’s.
Low control pressure supply. Replace pressure regulator if necessary.
Function speed switch malfunction. Replace switch.
Amperage too low on controller. Correctly adjust controller.
Defective pump, low oil volume. Repair or replace pump.
Poor response, function shuts off slowly
when command is removed.
Low spool spring preload. Check for correct spring and shims in end caps.
Sticking spool due to contamination. Remove end cap and check spool freedom.
Ramp set too high in controller. Adjust controller.
Sticking control handle. Repair or replace controller.
STEERING SYSTEM.
No response to steer control.
Circuit breaker open. Determine and correct cause; reset circuit
breaker.
Hydraulic system oil low. Replenish oil as necessary.
Hydraulic system pressure too low. Adjust pressure.
Damaged wiring on control switch or solenoid
valve. See proper wiring diagram.
Control switch not functioning properly. Replace switch.
Restricted or broken hydraulic line on valve
bank, hydraulic pump or rotary coupling. (If
equipped.) Clean, repair or replace line.
Table 3-4.Chassis Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY