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Hitachi EX100-2 Excavator Legacy and Electrical System Insights
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Hitachi’s Rise in the Excavator Market
The Hitachi EX100-2 is a mid-sized hydraulic excavator that emerged during a transformative period in Hitachi Construction Machinery’s global expansion. Founded in 1970 as a division of Hitachi Ltd., the company quickly became a dominant force in the excavator market, especially in Asia and Oceania. By the late 1980s and early 1990s, Hitachi had refined its EX-series to meet international demands for reliability, fuel efficiency, and ease of maintenance.
The EX100-2, introduced in the early 1990s, was part of the second-generation EX lineup. These machines were designed with improved hydraulic control, simplified electrical systems, and enhanced operator comfort. The EX100-2 was particularly popular in Southeast Asia, Australia, and parts of Europe, where its balance of power and compactness made it ideal for urban construction, roadwork, and agricultural applications.
Core Specifications and Performance
The EX100-2 typically features:
  • Operating weight: Approximately 10,000–11,000 kg
  • Engine: Isuzu 4BG1T, 4-cylinder turbocharged diesel
  • Horsepower: Around 70–75 HP
  • Bucket capacity: 0.4–0.5 m³
  • Hydraulic system pressure: ~30 MPa
  • Swing speed: ~12 rpm
This model’s turbocharged engine delivers consistent torque across a wide RPM range, making it suitable for trenching, lifting, and light demolition. Its hydraulic system, while not electronically controlled like later models, is known for smooth responsiveness and minimal lag.
Electrical System and Wiring Challenges
One of the most discussed aspects of the EX100-2 is its electrical system. Unlike newer excavators that rely heavily on CAN bus networks and multiplexed wiring, the EX100-2 uses a relatively straightforward analog wiring layout. However, due to age and exposure to harsh environments, many units experience issues such as:
  • Corroded connectors
  • Brittle insulation on wires
  • Faulty relays and fuses
  • Inconsistent sensor readings
Operators often seek wiring diagrams to troubleshoot problems with ignition, fuel solenoids, or hydraulic lockouts. These diagrams, originally provided in service manuals, are essential for diagnosing issues without relying on proprietary scan tools.
In one case from the Philippines, a contractor working on flood control projects in Mindanao reported intermittent engine shutdowns. After weeks of trial-and-error, the culprit was traced to a frayed wire near the starter relay. With a proper schematic and a multimeter, the issue was resolved in under an hour—highlighting the importance of accessible documentation.
Terminology Notes
  • Solenoid: An electromechanical device that converts electrical energy into linear motion, often used to control fuel flow or hydraulic valves.
  • Relay: A switch operated by electricity, allowing a low-power circuit to control a high-power load.
  • CAN Bus: A modern communication protocol used in vehicles and machinery to allow microcontrollers and devices to communicate without a host computer.
Maintenance Strategies and Operator Tips
To extend the life of the EX100-2, seasoned mechanics recommend:
  • Replacing all wiring harnesses exposed to heat or vibration every 10–15 years
  • Using dielectric grease on connectors to prevent corrosion
  • Installing aftermarket LED indicators to monitor voltage drops
  • Routinely checking ground points for continuity
In colder climates, battery voltage fluctuations can trigger false sensor readings. Installing a voltage stabilizer or upgrading to AGM batteries can mitigate these issues.
Hitachi’s Global Footprint and Production History
By the time the EX100-2 was phased out in the late 1990s, Hitachi had sold tens of thousands of EX-series excavators globally. The EX100-2 was produced in Japan and exported widely, with localized variants for Europe and Southeast Asia. Hitachi’s partnership with Fiat in Europe also led to co-branded models like the Fiat-Hitachi FH100, which shared many components with the EX100-2.
Hitachi Construction Machinery continues to innovate, with its ZX-series now incorporating hybrid systems, telematics, and autonomous operation. Yet, the EX100-2 remains a favorite among independent contractors and rural operators who value mechanical simplicity over digital complexity.
Restoration and Aftermarket Support
In recent years, the EX100-2 has gained popularity among restoration enthusiasts. Its mechanical design allows for full rebuilds without specialized software or dealer-only tools. Aftermarket suppliers in China, India, and the UAE offer replacement parts ranging from hydraulic pumps to electrical harnesses.
A restoration shop in Texas recently documented a full rebuild of a 1991 EX100-2, including rewiring, repainting, and retrofitting a modern seat and canopy. The machine was then used to clear land for a veterans’ memorial park—a fitting tribute to a workhorse that refuses to retire.
Conclusion
The Hitachi EX100-2 stands as a symbol of durable, operator-friendly design in an era before electronics dominated construction machinery. Its legacy continues through the hands of mechanics, operators, and restorers who appreciate its straightforward engineering and global impact. Whether digging trenches in England or clearing brush in the Philippines, the EX100-2 proves that good machines never fade—they just get rewired.
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