Troubleshooting Electrical Breaker Issues on the Hitachi EX120-2

[MikePhua]

The Hitachi EX120-2 is a reliable and widely used tracked excavator, known for its robust construction and high-performance capabilities. However, like all heavy equipment, it can encounter electrical issues that disrupt its functionality. One of the most common problems operators may face is an electrical breaker issue, which can lead to the machine shutting down unexpectedly or certain systems malfunctioning. Understanding the cause of these issues and knowing how to troubleshoot them is essential to minimize downtime and avoid costly repairs.
Understanding the Electrical System in the Hitachi EX120-2
Before diving into troubleshooting, it's important to understand the basic structure of the EX120-2’s electrical system. The electrical system is composed of various components that work together to control the engine, hydraulic systems, lights, and other machinery functions. These include:

• Main Electrical Panel: Houses the circuit breakers, fuses, and relays that control the power flow to the different systems.
  
• Battery and Charging System: Provides the initial power needed to start the engine and maintains power for auxiliary systems.
  
• Control Modules: These include the engine control unit (ECU) and hydraulic control units (HCU), which regulate the functions of the engine, hydraulics, and transmission.
  
• Sensors and Actuators: These provide real-time feedback to the control systems to adjust performance based on operational conditions.
  

The electrical breaker in the Hitachi EX120-2 is a crucial safety component that prevents overheating or electrical surges by cutting off the power in the event of a fault. If the breaker keeps tripping, it is often a sign that there is an underlying electrical problem that needs to be addressed.
Common Causes of Electrical Breaker Issues

1. Overloaded Circuit
   • One of the primary reasons for the breaker tripping is an overloaded circuit. If the electrical system is drawing more current than the breaker can handle, it will automatically trip to protect the system.
     
   • Symptoms: Frequent tripping of the breaker, particularly when certain systems or components are engaged (such as the hydraulic system or lights).
     
   • Diagnosis: Check the electrical load of the system to ensure it is within the acceptable range. Identify any components that may be drawing excessive current, such as faulty motors or pumps.
     
2. Short Circuits
   • Short circuits can occur when two wires that should remain separate come into contact with each other, creating a direct path for current to flow without any resistance. This can result in overheating and cause the breaker to trip.
     
   • Symptoms: Sudden, unexpected trips of the electrical breaker, often when the machine is under load or when specific components are turned on.
     
   • Diagnosis: Visually inspect the wiring harnesses and connections for any signs of damage, wear, or exposed wires that could be shorting out. Use a multimeter to check for continuity between wires that shouldn’t be connected.
     
3. Damaged Wiring or Connections
   • Over time, the wiring and electrical connectors on the EX120-2 can become worn or damaged, especially in areas exposed to heat, moisture, or physical wear and tear. Damaged wires or loose connections can cause electrical arcing, leading to breaker trips.
     
   • Symptoms: Intermittent power loss, systems cutting in and out, or the breaker tripping after the machine is in operation for a while.
     
   • Diagnosis: Inspect the entire electrical system for any damaged, frayed, or burnt wires. Pay close attention to the areas around the electrical panel, battery connections, and any exposed cables that may be subject to wear.
     
4. Faulty Electrical Components
   • Faulty components such as relays, solenoids, or sensors can cause electrical breakers to trip. If a component malfunctions and starts drawing excessive power, it can trigger the breaker to shut down the system.
     
   • Symptoms: The breaker trips when a specific function, such as the hydraulic system or engine control, is activated.
     
   • Diagnosis: Isolate the faulty component by methodically disconnecting or bypassing electrical systems and observing if the breaker still trips. If a specific system or component causes the breaker to trip, this may indicate a problem with the component.
     
5. Incorrect Fuse or Breaker Rating
   • If the electrical breaker is rated too low for the machinery's needs, it will trip frequently even under normal operating conditions.
     
   • Symptoms: Frequent trips of the breaker, especially when the equipment is operating normally.
     
   • Diagnosis: Check the specifications for the electrical breaker and compare it to the equipment's electrical load requirements. If the breaker is undersized, replace it with the correct one that matches the system's power demands.
     

Step-by-Step Troubleshooting Guide

1. Inspect the Circuit Breaker and Fuses
   • Begin by visually inspecting the circuit breaker and any fuses associated with the electrical system. Look for signs of physical damage, overheating, or corrosion.
     
   • Solution: Replace any blown fuses or damaged breakers. If the breaker trips again after replacement, the problem may lie elsewhere in the system.
     
2. Check for Overloaded Circuits
   • Check the electrical load of the machine. Start by turning off all auxiliary systems and devices and then attempt to engage the machine. If the breaker does not trip, the issue may lie with one of the added components.
     
   • Solution: Isolate the suspect component, such as lights, hydraulic pumps, or any electrical attachments, and check if the breaker still trips when these systems are used.
     
3. Look for Short Circuits
   • Examine the wiring for any visible signs of wear, chafing, or physical damage. Check for any places where the wires may be rubbing against metal parts of the machine.
     
   • Solution: If a short is detected, repair or replace the damaged wires. Ensure that wiring is properly insulated and routed to avoid further damage.
     
4. Test Electrical Components
   • Test electrical components such as relays, solenoids, and sensors to ensure they are working properly. Use a multimeter to check for proper voltage and resistance.
     
   • Solution: Replace any faulty components that are drawing excessive power and causing the breaker to trip.
     
5. Evaluate the Breaker’s Rating
   • Verify that the circuit breaker is rated appropriately for the machine’s electrical system. If it is too small, it will trip more easily, even under normal load.
     
   • Solution: Replace the breaker with one that is correctly rated for the machine’s electrical needs.
     

Preventive Maintenance Tips

1. Regular Inspections
   • Conduct routine inspections of the electrical system, including wiring, connections, fuses, and breakers. Regular checks can identify early signs of wear or damage before they become major issues.
     
2. Use Quality Components
   • Always use high-quality, manufacturer-recommended parts for repairs and replacements. Using inferior components can lead to further electrical problems and breakdowns.
     
3. Keep Connections Clean and Tight
   • Over time, dirt, moisture, and corrosion can affect electrical connections. Ensure that all terminals and connectors are clean and tightly secured to prevent intermittent connections or short circuits.
     
4. Ensure Proper Load Management
   • Avoid overloading the electrical system by operating within the recommended parameters. Use auxiliary equipment that is appropriately sized for the machine’s electrical output.
     

Conclusion
Electrical breaker issues in the Hitachi EX120-2 can be caused by a variety of factors, including overloaded circuits, short circuits, faulty components, or incorrectly rated breakers. Through a systematic troubleshooting process, it is possible to identify and resolve the issue, minimizing downtime and avoiding costly repairs. By performing regular maintenance and being proactive about inspections, operators can ensure that their EX120-2 remains in optimal working condition. Understanding the electrical system, knowing how to diagnose common issues, and performing proper preventive care are key to ensuring long-term reliability and performance.