Hitachi EX120 Joystick Thumb Button Wiring Issue Solution

[MikePhua]

During operation of the Hitachi EX120 excavator, some users have encountered issues where the thumb button on the joystick does not work or malfunctions. This is often caused by wiring issues. Below, we will break down the possible causes and solutions.
Problem Symptoms
Users have reported that the thumb button on the joystick is unresponsive, preventing normal operation. The thumb button typically controls auxiliary functions, such as the bucket tilt or the drive functions. This issue is commonly observed in machines that have been in use for an extended period or when wiring connections are improperly maintained.
Possible Causes

1. Loose or Damaged Wiring: The wiring connected to the joystick button may have become loose or damaged over time due to frequent use, causing a poor connection or breakage.
   
2. Joystick Controller Failure: The internal circuit of the joystick itself may have failed due to prolonged use.
   
3. Grounding Issues: The ground connection for the joystick button may have become loose or damaged, leading to failure in signal transmission.
   

Troubleshooting Steps

1. Check the Button Wiring: First, turn off the machine to ensure safety. Afterward, inspect the wiring of the thumb button to see if it has become loose or damaged. Use a multimeter to check for continuity and ensure that there are no broken connections.
   
2. Inspect the Joystick Controller: If the wiring appears intact, the issue may be with the joystick controller itself. Consider disassembling the joystick to check the internal circuitry for any damaged components. If the controller is faulty, it may need to be replaced.
   
3. Check the Grounding Connection: Inspect the ground wire for the joystick button to ensure it is properly connected. Poor grounding can cause the button to fail to transmit signals properly. Ensure that the ground wire is secure and free from corrosion.
   
4. Replace the Button: If the button itself is damaged, it may need to be replaced. Test the functionality of the button when it’s in good condition to ensure it sends signals correctly.
   

Solution

1. Repair the Wiring: Fix any loose or damaged wiring to restore proper button functionality.
   
2. Replace the Controller: If the joystick controller is found to be faulty, consider replacing it.
   
3. Ensure Proper Grounding: Ensure the ground connection is secure and intact to avoid button malfunction due to poor grounding.
   

By following these checks and repairs, the issue with the Hitachi EX120 joystick thumb button can typically be resolved. If the problem persists, professional repair support may be required.