JLG 15/20MSP Service Manual - Manual (Page 166)

SECTION 6 - TROUBLESHOOTING
6-46 – JLG Lift – 3121231
Machine 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 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.
Table 6-54. Machine Won’t Drive Straight.
STEP ACTION SPEC YES NO
1. Check for the following on the drive assembly, drive attachment weldments;
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 hardware; is
hardware loose. — Repair/Replace/
Tighten component
Go to Step 4
4. Check the left and right drive motor brakes for loose hardware & not releas-
ing properly. — Tighten or Adjust
per procedure
in this
Service Manual
Go to Step 5
5. Is the electrical signal and amperage draw to the drive motors equal? Check
with machine on level surface. See Table 6-3. Recheck Steps
1 thru 5
Go to Step 6
6. Check the drive motor brushes, do they need replaced? — Replace per
procedure in this
Service Manual
Go to Step 7
7. Is joystick control defective?
If possible, swap out with another platform control. — Repair/Replace
Platform control
Go to Step 8
8. Is the Traction Control Module defective or connections not tight?
If possible, swap out with another Traction Control Module. — Tighten Connec-
tions or Replace
Traction Control
Module
Go to Step 9
9. Inside the drive motor gear box check if; the drive shaft is excessively loose
& condition of drive shaft bearings.
Are any gears broken or gear teeth excessively worn. — Repair/Replace gear box
components per procedure in this Service
Manual