JLG 40H Service Manual - Manual (Page 122)

SECTION 3 - TROUBLESHOOTING
3-10
– JLG Lift – 3120240
TROUBLE PROBABLE CAUSE REMEDY
REAR FRAME AXLE AREA.
Difficulty encountered when moving machine. Load capacity exceeded.
Flow divider sticking.
Machine being moved up too steep a grade.
Grade too steep.
Drive wheel tire treads worn smooth.
Drive brakes “dragging”.
System pressure too low.
Drive hub(s) defective.
Engine RPM not set.
Counterbalance valve defective.
Accessory valve not adjusted properly.
Low amperage on controller.
Reduce load. Apply loads only in accordance with
load capacity indicator.
Repair or replace flow divider.
Remove machine from grade and check that drive
system operates correctly.
See Caution Placard on platform for specified
grades and sideslips.
Replace tires as necessary and inflate to specified
pressure.
Re-adjust pressure.
Re-adjust pressure.
Repair or replace hub.
Correctly set engine RPM.
Replace counterbalance valve.
Correctly adjust accessory valve.
Correctly adjust controller.
DRIVE SYSTEM.
No response to control. Hydraulic system oil low.
Hydraulic pump not functioning properly.
Restricted or broken pump supply line.
Restricted or broken line on valve bank or rotary
coupling.
Drive hub(s) disconnected.
Rotary coupling leaking internally. (Seal(s) worn.)
Drive motor(s) not functioning properly.
Air in wheel brake circuit.
Damaged wiring on control switch.
Control switch not functioning properly.
Brake(s) not releasing.
Replenish oil as necessary.
Repair or replace pump.
Clean, repair or replace line.
Clean, repair or replace line.
Reconnect disconnect cap on hub.
Repair or replace coupling.
Repair or replace motor(s).
Bleed circuit. determine and correct cause.
Repair or replace wiring.
Replace switch.
Determine cause and repair or replace.