JLG 120HX ANSI Service Manual - Manual (Page 89)

SECTION 3 - TROUBLESHOOTING
3120686 – JLG Lift – 3-7
Boom leaks down.
Holding valve sticking. Replace holding valve.
Damaged cylinder. Repair or replace cylinder.
BOOM SWING SYSTEM
No response to swing control.
Swing function not activated within 7 seconds
after footswitch was depressed. Recycle footswitch.
Hydraulic system oil low. Replenish oil as necessary.
Swing control switch not functioning. Repair or replace swing control switch.
Restricted or broken supply line on valve bank or
hydraulic pump. Clean or replace line.
Control valve not functioning properly. Repair or replace valve.
Swing motor not functioning properly. Repair or replace motor.
Restrictor valve(s) plugged. Clean or replace restrictor valve.
Foreign objects(s) wedged between swing
motor pinion and swing gear. Remove objects, check for damage, and repair
or replace component(s) as required.
Pressure reducing valve in swing circuit malfunc-
tioning. Repair or replace pressure reducing valve.
No electric power to valve. See proper wiring diagram.
Boom will swing in one direction only.
Restricted or broken hydraulic line or fitting. Clean, repair, or replace line or fitting.
Control valve not functioning properly. Repair or replace valve.
Foreign object(s) wedged between swing motor
pinion and swing gear. Remove object(s), check for damage and repair
or replace component(s) as required.
Swing control switch not functioning properly. Repair or replace swing control switch.
Boom swings erratically in either direction.
Hydraulic system oil low. Replenish oil as necessary.
Lack of lubricant on swing gear or speed reducer
pinion. Lubricate as required. (See Lubrication Chart.)
Swing motor not functioning properly. Repair or replace swing control switch.
Worn or broken teeth on swing gear or swing
motor pinion. Replace gear(s) as required.
Restrictor valves(s) plugged. Clean or replace restrictor valve.
Table 3-2.Boom Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY