JLG 20VP (3120728) Service Manual - Manual (Page 88)

SECTION 3 - TROUBLESHOOTING
3-28 – JLG Lift – 3120728
Won’t Drive Straight
Overview Of Procedure
The following procedure examines the drive motor assembly weldments attaching the drive motors to the base frame. Also
internal components of the the drive motors, gear box and a check of the components between the gear box and the drive
wheels.
Check For These Obvious Conditions First:
• Battery voltage 24 volts. (Fully charge batteries)
• Nothing is lodged between one of the wheels and the base frame.
• A caster wheel on the front of the machine is seized up, creating resistance.
• Joystick properly calibrated per procedure in Section-2 of Service Manual.
Table 3-18. Won’t Drive Straight.
STEP ACTION SPEC YES NO
1. Check for the following on the drive assembly, drive attachment
weldment; is bent, has broken welds, or loose hardware.
—
Repair/Replace/
Tighten weldment
Go to Step 2
2. Check for the following on the drive assembly, drive motor mounting
plates; are bent, are square with drive weldments, or is hardware
loose?
—
Repair/Replace/
Tighten weldment
Go to Step 3
3. Check for the following on the drive assembly, drive motor hard-
ware; is hardware loose, flange bearing - bad/loose, slip clutch -
check torque settings or adjustment.
—
Repair/Replace/
Tighten compo-
nent
Go to Step 4
4. Check the left and right drive motor brakes for loose hardware & not
releasing properly.
—
Tighten or Adjust
per procedure
in this
Service Manual
Go to Step 5
5. Inside the drive motor gear box check if; the drive shaft is exces-
sively loose & conditon of drive shaft bearings.
Are any gears broken or gear teeth excessively worn.
—
Repair/Replace
components per
procedure in this
Service Manual
Go to Step 6
6. Is the electrical signal and amperage draw to the drive motors
equal? 24 volts
15 amps
Recheck Steps
1 thru 5
Go to Step 7
7. Check the drive motor brushes, do they need replaced?
—
Replace per
procedure in this
Service Manual
Go to Step 8
8. Is the X102 wiring harness (from platform contol box to MC-1 box)
damaged, check wiring harness visually and individual wires with
ohm meter.
—
Repair or Replace
Harness as
Required
Go to Step 9
9. Is joystick control defective?
If possible, swap out with another platform control.
—
Repair/Replace
Platform control
Go to Step 10
10. Is MC-1 control box defective or connections not tight?
If possible, swap out with another MC-1 control box.
—
Tighten Connec-
tions or Replace
MC-1 box
—