JLG M450 ANSI Service Manual - Manual (Page 227)

SECTION 7 - BASIC TROUBLESHOOTING, ELECTRICAL INFORMATION, & SCHEMATICS
3121127 – JLG Lift – 7-13
Proportional Flow Valve not functioning properly. Repair or replace valve.
Hydraulic pump not functioning properly. Repair or replace pump.
Personality Settings Incorrect. Adjust settings.
Steer cylinder not functioning properly. Repair or replace cylinder.
Steering inoperative.
Damaged wiring on control switch or solenoid
valve. See proper wiring diagram/Run System Test.
Solenoid valve not functioning properly. Repair or replace valve.
Control switch not functioning properly. Replace switch/Run System Test.
Relief valve improperly set or not functioning
properly. Reset, repair or replace valves as required.
Steer cylinder not functioning properly. Repair or replace cylinder.
Machine will not steer left or to the right.
Wiring on control switch is damaged. See proper wiring diagram/Run System Test.
Wiring on solenoid valve damaged. Repair or replace wiring/Run System Test.
Coil in solenoid damaged. Replace coil.
No oil flow or pressure to steer circuit. Take pressure reading at steer valve and adjust
as necessary.
Bent cylinder rod. Repair or replace cylinder.
Damaged tie rod. Replace tie rod.
Cylinder packing defective. Repair or replace cylinder.
Machine wanders; steering not firm.
Crossover relief valve set too low or not function-
ing properly. Reset, repair or replace valve as required.
Steer linkages loose. Tighten linkage.
Steer wheel toe-in not set properly. Adjust toe-in for 1/4 inch overall.
Spindle bushings badly worn. Replace bushings.
DRIVE BRAKE.
Brake Slips
Excessive pressure in hydraulic system. Check hydraulic filter, restrictions in other
hydraulic components.
Disc plates worn. Check disc thickness.
Springs broken or have taken a permanent set. Check release pressure.
Table 7-4. Chassis Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY