Bobcat 6679905 is a right‑hand selectable joystick control unit used on A220, A300, S100–S330 loaders and T110–T320 track loaders. Common failure modes for this class of handheld controllers include worn potentiometers causing erratic speed or direction response, broken selector switches leading to stuck positions, and internal solder joint fatigue in the microcontroller board. Begin troubleshooting by verifying that the controller’s power supply voltage is within spec (typically 24 V DC) and checking for any blown fuses; inspect the joystick shaft and selector switch for mechanical wear or debris; then review any diagnostic error codes displayed on the operator interface, and finally test the potentiometer resistance range with a multimeter to confirm proper operation.[oss-gpt-20b]