JLG 120HX ANSI Service Manual - Manual (Page 95)

SECTION 3 - TROUBLESHOOTING
3120686 – JLG Lift – 3-13
Drive wheel tire treads worn smooth. Replace tires as necessary and inflate to speci-
fied pressure.
Drive brakes "dragging". Re-adjust pressure.
System pressure too low. Re-adjust pressure.
Drive hub(s) defective. Repair or replace hub.
Engine RPM’s not set. Correctly set engine RPM.
Drive motors worn. Repair or replace drive motors.
Counterbalance valve defective. Replace counterbalance valve.
Low amperage on controller. Correctly adjust controller.
DRIVE SYSTEM.
No response to control.
Drive function not activated within 7 seconds
after footswitch was depressed. Recycle footswitch.
Hydraulic system oil low. Replenish oil as necessary.
Hydraulic pump not functioning properly. Repair or replace pump.
Restricted or broken pump supply line. Clean, repair or replace line.
Restricted or broken line on valve bank. Clean, repair or replace line.
Drive motor(s) not functioning properly. Repair or replace motor(s).
Air in wheel brake circuit. Bleed circuit, determine and correct cause.
Fuse is blow-out on control card. Replace fuse.
Damaged wiring on control switch. Repair or replace wiring.
Control switch not functioning properly. Replace switch.
Brake(s) not releasing. Determine cause and repair or replace.
Machine will not travel in forward.
Hydraulic system oil low. Replenish oil as necessary.
Restricted or broken hydraulic line or fitting. Clean, repair or replace line or fitting.
Control valve not functioning properly. Repair or replace valve.
Drive motor(s) not functioning properly. Repair or replace motor(s).
Circuit breaker open. Determine and correct cause; reset circuit
breaker.
Counterbalance valve sticking on return side. Adjust return counterbalance out 3 turns - cycle
drive - return to original position.
Table 3-4.Chassis Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY