Changing Control Patterns on Hitachi EX120-3 Excavators

[MikePhua]

Hitachi EX120-3 Development and Market Reach
The Hitachi EX120-3 hydraulic excavator was introduced in the late 1990s as part of Hitachi Construction Machinery’s third-generation EX series. Designed for mid-size earthmoving and utility work, the EX120-3 features a 12-ton operating weight, a 4-cylinder Isuzu diesel engine producing around 90 hp, and a robust hydraulic system capable of precise control and efficient digging. Hitachi, founded in 1970 as a standalone construction division, has sold hundreds of thousands of excavators globally, with the EX series being particularly popular in Asia, North America, and Australia.
The EX120-3 was built with a focus on mechanical simplicity and operator comfort. Its pilot-controlled joysticks and modular valve blocks made it easier to service and modify, which became a key advantage in markets where control pattern preferences vary.
Terminology Annotation

• Pilot Lines: Low-pressure hydraulic lines that transmit joystick input to control valves. They do not power the actuators directly but signal the main valve bank.
  
• Selector Valve: A multi-position valve that reroutes pilot signals to change joystick behavior. Typically used to switch between control patterns.
  
• Slew: The rotational movement of the upper structure of the excavator, often referred to as swing.
  

Why Control Patterns Matter
Excavator operators are trained on specific control layouts. In North America, the John Deere pattern is common, with boom and swing on the left joystick and stick and bucket on the right. In contrast, the Caterpillar pattern places stick and bucket on the left and boom and swing on the right. Switching between these layouts without retraining can lead to operational errors, safety risks, and reduced productivity.
The EX120-3 includes a selector valve intended to toggle between patterns. However, in some units—especially those imported from Japan or configured for regional standards—the valve does not fully reassign all functions. This partial changeover can result in mismatched controls, such as bucket curl remaining on the left joystick while swing shifts to the right.
Diagnosing Incomplete Changeover
In one case, an operator attempted to switch from Cat to John Deere pattern using the selector valve. The result was a hybrid layout: bucket curl on the left and slew on the right. This indicated that the selector valve was either misconfigured or had been previously modified. Upon inspection, it was discovered that the machine had been retrofitted with pilot lines rerouted manually—likely by a previous owner or importer.
To correct the issue, the operator reverted to the original control pattern and manually swapped pilot lines at the manifold block beneath the cab. These lines were labeled A through H, and the correct reassignment required a cross-pattern swap: top left to bottom right and top right to bottom left.
Recommendations for Safe and Accurate Reconfiguration

• Before making changes, document the current control pattern and label all pilot lines
  
• Use colored zip ties or numbered tags to avoid confusion during reassembly
  
• Consult the hydraulic schematic for the EX120-3 to identify joystick-to-valve mappings
  
• If the selector valve has multiple positions, test each one and record the resulting control behavior
  
• Avoid relying solely on the selector valve if the machine has been modified or is a grey-market import
  

Grey-Market Machines and Regional Variants
Many EX120-3 units in North America are grey-market imports—machines originally built for Japanese domestic use and later resold overseas. These units often have JIS (Japanese Industrial Standard) control configurations and may lack full support for SAE or ISO patterns. The selector valve in such machines may offer four positions, but only two may be functional due to internal porting limitations.
In Australia, similar issues have been reported with JCB and Komatsu machines, where operators had to manually reassign pilot lines to match local training standards. Some dealers now offer retrofit kits with pre-labeled hoses and updated selector valves to simplify the process.
Field Anecdotes and Practical Advice
A quarry operator in Ontario recalled receiving a Hitachi EX120-3 with mismatched controls. After days of trial and error, he discovered that the valve block under the cab had been modified with non-standard fittings. By tracing each pilot line and comparing joystick movement to actuator response, he restored the correct pattern and trained his crew accordingly.
In Maine, a contractor successfully changed over his EX120-3 by swapping pilot lines at the manifold. He noted that the joystick itself does not control pump flow—this is managed by a switch on the main valve bank. Understanding this distinction helped him avoid unnecessary electrical troubleshooting.
Conclusion
Changing control patterns on the Hitachi EX120-3 is possible but requires careful inspection, documentation, and sometimes manual intervention. While the selector valve offers convenience, it may not function as expected on modified or imported units. By understanding pilot line routing and control logic, operators can safely reconfigure their machines to match preferred patterns and maintain operational consistency. With proper labeling and attention to hydraulic schematics, even legacy excavators like the EX120-3 can be adapted to modern jobsite standards.