JLG 40H Boom Swing Not Moving in Creep Mode

[MikePhua]

The JLG 40H is a versatile diesel-powered boom lift designed for various industrial applications. One of its key features is the "creep mode," which allows for slow and precise movements, particularly useful when working in tight spaces or performing delicate tasks. However, some operators have reported issues where the boom swing function does not operate in creep mode, even though other functions like drive and main lift work as expected.
Understanding Creep Mode
Creep mode is a feature that reduces the operational speed of the machine's functions, providing the operator with finer control. To activate creep mode on the JLG 40H, the operator turns the function speed control knob all the way counterclockwise until it clicks. This action should reduce the speed of drive, main lift, tower lift, platform rotate, and swing functions. If the boom swing does not respond in this mode, it indicates a potential issue that requires attention.
Potential Causes for the Issue
Several factors could contribute to the boom swing not functioning in creep mode:

1. Wiring and Connector Issues: Loose or damaged wires and connectors, especially those related to the swing controller, can disrupt the signal transmission necessary for the boom swing to operate in creep mode.
   
2. Calibration Problems: The controllers on the JLG 40H need to be calibrated to ensure proper communication with the valve solenoids. If the calibration is off, the analog signal in creep mode may not be sufficient to move the valve spool, preventing the boom swing from operating.
   
3. Control Console Exposure to Moisture: Exposure to rain or moisture can cause erratic behavior in the controls. For instance, if the control console gets wet, the lift may behave unpredictably, such as moving forward unexpectedly.
   
4. Joystick Potentiometer Labels: The potentiometer labels on the joysticks can wear off over time, leading to confusion about the joystick's function. For example, if the labels for "low" and "RPM" are missing, the operator might inadvertently operate the wrong function.
   

Diagnostic and Troubleshooting Steps
To address the issue of the boom swing not moving in creep mode, consider the following steps:

1. Inspect Wiring and Connectors: Check the wiring and connectors leading to the swing controller for any signs of damage or loose connections. Ensuring these are intact can resolve communication issues.
   
2. Verify Calibration: Consult the JLG service manual to understand the calibration procedure for the controllers. Proper calibration ensures that the analog signals are correctly interpreted, allowing the boom swing to function in creep mode.
   
3. Protect the Control Console: Keep the control console dry to prevent erratic behavior. Consider installing protective covers or using the machine in sheltered areas to minimize exposure to moisture.
   
4. Check Joystick Labels: Inspect the potentiometer labels on the joysticks. If they are worn or missing, replace them to ensure the operator can correctly identify each joystick's function.
   

Conclusion
The JLG 40H's boom swing not operating in creep mode can be attributed to various factors, including wiring issues, calibration problems, moisture exposure, and joystick label wear. By systematically addressing these potential causes, operators can restore full functionality to the boom swing in creep mode, enhancing the machine's precision and safety during operations.