JLG DVSP Series Service Manual - Manual (Page 147)

SECTION 6 - TROUBLESHOOTING
3121136 – JLG Lift – 6-33
6.10 MAST TROUBLESHOOTING
Platform Will Not Lower Manually
Check For These Obvious Conditions First:
• Is there an obstruction in the mast assembly?
• Is there a restricted hydraulic line (smashed)?
• Are the mast slide pads shimmed properly (not too tight), per Mast Assembly procedure in Service Manual?
Platform Lift Up And Down Jerky
Overview Of Procedure
The following procedure suggests areas on the machine which might attribute to erratic movement of the platform during lift
up and down.
Check For These Obvious Conditions First:
• If mast is not running smooth or has tight and rough spots, refer to the Mast Section Rebuild.
• Hydraulic oil level in reservoir tank at full level.
• Hydraulic oil is not milky (presence of water), or foamy (full of air).
Table 6-41. Platform Will Not Lower Manually.
STEP ACTION SPEC YES NO
1. Check to see of the platform will lower from the Ground Control Sta-
tion in Ground Control Mode.
—
Repair or Replace
the Manual
Descent Control
Valve
Go to Step 2
2. Check to see if the lift down valve is opening completely.
— Go to Step 3
Replace the Lift
Down Valve
3. Check the flow valve in the lift cylinder for a restriction.
—
Clean or Replace
Flow Valve
Consult Factory
Table 6-42. Platform Lift Up and Down Jerky
STEP ACTION SPEC YES NO
CONTROLS (ELECTRICAL)
1. Is platform control console, platform enable, up or down pad defec-
tive or worn out?
— Replace pad Go to Step 2
2. Loose connections, ground and power.
—
Repair
connection
Go to Step 3
3. Valve solenoid keeps opening and closing.
—
Repair Connec-
tion or Replace
Valve
Go to Step 4
4. Problem internal to the Ground Control Module. — Replace Module Go to Step 5
HYDRAULIC
5. Is the hydraulic valve working properly. — Go to Step 6 Replace Valve
6. Pump drive cavatating. — Replace Pump Go to Step 7
7. Lift cylinder
—
Rebuild or
Replace Cylinder
—