JLG 20VP (3120728) Service Manual - Manual (Page 94)

SECTION 3 - TROUBLESHOOTING
3-34 – JLG Lift – 3120728
Platform Will Not Lift Up From Ground Control Toggle Switch
Overview Of Procedure
The following procedure examines the complete ground control circuit from the battery all the way to the pump motor for
wiring or components which could be causing a failure of that circuit.
Check For These Obvious Conditions First:
• Battery voltage 24 volts. (Fully charge batteries)
• Battery connections clean and tight.
• Key switch positioned to Ground (GRND) control.
• Emergency stop switch pulled out. (Reset Position)
• Ground control power supply and wiring, OK (Table 3-4).
• Manual descent valve closed.
• 5 amp fuses on power and pump circuits, OK.
• Hydraulic oil level, OK.
• Weight in platform does not exceed machine maximum capacity.
Table 3-24. Unit Will Not Lift Up From Ground Control Toggle Switch.
STEP ACTION SPEC YES NO
1. Does the pump motor run when lift up is selected at the ground con-
trol switch?
Note: Steps 2 thru 9 are to be performed with LIFT UP selected at the
ground control.
—
Go to Steps 5,6
and 10
Check Ground
Power Circuit
(Table 3-4)
Before Continu-
ing to Step 3
2. Check terminal 30 and 85 on the ground control relay for ground. Is
ground contact OK?
Ground Go to Step 3
Repair Wiring or
Connection
3. Check continuity across terminals 87 and 30 on the ground control
relay. Is there continuity? (Relay must be energized)
— Go to Step 4 Replace Relay
4. Check the Black wire from terminal 87 on the ground control relay to
the lift up/down ground control switch. Is there continuity with B –?
— Go to Step 5
Repair Wiring or
Connection
5. Check for continuity across the terminals (Black to Tan 3-1 and Tan
55-1) of the lift up/down ground control toggle switch. Is there con-
tinuity?
— Go to Step 6
Replace Lift Up/
Down Ground
Control Switch
6. Check the Tan, 3-1 wire for continuity from the lift up/down ground
switch to the lift up coil. Is there continuity?
— Go to Step 7
Repair Wiring or
Connection
7. Check the Tan, 55-1 wire from the lift up/down ground switch to the
pump contactor for continuity. Is there continuity?
— Go to Step 8
Repair Wiring or
Connection
8. Check the Yel/Red, 2-6 wire from the pump motor to the pump con-
tactor and lift-up coil for voltage. Is there voltage?
24 Volts Go to Step 9
Repair Wiring or
Connection
9. Check the wire from the lift switch (Tan 55-1) pump contactor to the
battery (-) terminal for continuity. Is there continuity?
— —
Repair Wiring or
Connection
10. Check the pump motor pressure relief setting. Is it within specifica-
tion per Service Manual?
— Set as Required