JLG 20VP (3120728) Service Manual - Manual (Page 81)

SECTION 3 - TROUBLESHOOTING
3120728 – JLG Lift – 3-21
Table 3-8. Brake Limit Switch Circuit Check
STEP ACTION SPEC YES NO
1. Check for ground into the switch from the ground connection on the
left brake limit switch.
— Go to Step 2
Repair
Connection
2. Check for ground on the 49-4 wire coming out of left brake limit
switch.
— Go to Step 3
Adjust/Replace
Switch
3. Check for ground on the 49-4 wire going into the right brake limit
switch.
— Go to Step 4
Repair/Replace
49-4 wire
4. Check for gound on the 49-3 side of the right brake limit switch.
—
Replace
MC-1 box
Repair wire or
Connection
Table 3-9. Drive Motor/Circuit Check
• Perform these checks with the joystick enabled and pushed to the full forward position.
STEP ACTION SPEC YES NO
1. Check for 24 volts at the drive motor on the 55-3 wire on the right
motor and the 55-7 wire on the left drive motor. (Positive Side)
24 volts
Problem with
Motor
Go the Step 2
2. Check for 24 volts at the 55-3 wire at the X104 connector, pin A2 (for
right motor) and the 55-7 wire at the X103 connector, pin A1 (for left
motor).
24 volts
Check wiring and
connections
Problem in MC-1
box or Joystick
Table 3-10. Brake Switch/Circuit Check
• Perform these checks with the joystick enabled and pushed to the full forward position.
STEP ACTION SPEC YES NO
1. Check for 24 volts at the wiring connectors on the 55-4 wire on the
right drive motor brake unit and the 55-8 wire on the left drive motor
brake unit.
24 volts
Clean, Gap or
Replace Brake
Unit
Go to Step 2
2. Check for 24 volts at the 55-4 wire at the X104 connector, pin 5(for
right motor) and the 55-8 wire at the X103 connector, pin 5 (for left
motor).
24 volts
Check wiring and
connections
Problem in MC-1
box or Joystick