JLG 450A Service And Maintenance Manual page 86

SECTION 3 - TROUBLESHOOTING
.
TROUBLE
Automatic leveling inoperative.
Platform will not maintain level attitude.
No response to platform leveling controls.
Platform will not adjust "up" or "down" to level.
3-2
Table 3-1.Platform Assembly - Troubleshooting
PROBABLE CAUSE
Hydraulic system oil low.
Dual check valves dirty/inoperative.
Restricted or broken hydraulic line or fitting on
slave cylinder or main lift cylinder.
Worn seal(s) in slave level or main lift cylinder.
Counterbalance valve in slave cylinder defec-
tive.
Slave level or main lift cylinder not functioning
properly.
Counterbalance valve on slave leveling cylinder
improperly adjusted or not functioning properly.
Worn seal(s) in slave level or main lift cylinder.
Damaged slave level or main lift cylinder.
Level function not activated within 7 seconds
after footswitch was depressed.
Level control switch inoperative.
Hydraulic system oil low.
System orifice plugged/dirty.
Restricted or broken hydraulic line or fitting.
Control valve not functioning properly.
No electric to dump or control valve.
Slave cylinder not functioning properly.
Hydraulic pump not functioning properly.
Restricted or broken hydraulic line or fitting.
Slave cylinder not functioning properly.
Electrical failure.
Orifice plugged.
– JLG Lift –
REMEDY
Replenish oil as necessary.
Clean or replace as necessary.
Clean, repair, or replace line or fitting.
Replace seal(s).
Replace counterbalance valve.
Slave level or main lift cylinder not functioning
properly.
Replace valve.
Replace seal(s).
Repair or replace cylinder.
Recycle footswitch.
Repair or replace control switch lever.
Replenish oil as necessary.
Clean orifice.
Clean, repair, or replace line or fitting.
Repair or replace valve.
See proper wiring diagram.
Repair or replace pump.
Repair or replace pump.
Clean, repair, or replace line or fitting.
Repair or replace cylinder.
See proper wiring diagram.
Clean orifice.
3120869