First, check the drive engagement system in the handle. The switch actuator (part 202-13 or 202-21) connects to the switch electric assembly (part 202-17). If the actuator is broken or disconnected, the drive signal never reaches the motor.
- Inspect the control handle set (part 202-22 or 202-404). Look for a broken plastic actuator.
- Check the internal wire assembly (part 202-6) for a disconnected or pinched wire.
If the handle components are intact, the fault is in the self-propelled unit. The DC motor (part 201-8) within the motor & gear assembly (203-2) may have failed. You'll need to test for power at the motor connections when the drive switch is engaged.
Also verify the compression springs (part 202-18 or 202-16) that return the drive lever aren't broken, causing the switch to stay disengaged.