Diagnosing Angle Sensor Issues on the Hitachi EX100-2 Excavator

[MikePhua]

Quick Summary
The angle sensor on the Hitachi EX100-2 controls the swash plate position of the hydraulic pump, directly affecting flow output and machine responsiveness. Faulty readings or misadjustment can lead to sluggish hydraulics, engine bogging, or erratic performance under load.
Hitachi EX100-2 Background and Hydraulic Control System
The Hitachi EX100-2 was introduced in the early 1990s as part of Hitachi’s second-generation excavator lineup. It featured a refined hydraulic system with electronic control enhancements, including pump displacement regulation via an angle sensor. This sensor monitors the swash plate angle inside the variable displacement pump, allowing the machine to adjust flow based on operator demand and load conditions.
The EX100-2 became popular in Asia, North America, and Australia, with thousands of units sold. Its compact size and reliability made it a favorite among contractors and rental fleets. However, its early electronic systems—especially the angle sensor and solenoid controls—require precise calibration and are prone to age-related faults.
Symptoms of Angle Sensor Malfunction

• Engine bogs under load
  When the sensor misreads swash plate position, the pump may overstroke, demanding excessive torque from the engine.
  
• Hydraulics slow or unresponsive
  Incorrect voltage signals can prevent the pump from delivering adequate flow, especially during multi-function operations.
  
• Erratic behavior during warm-up
  Temperature-sensitive components may shift readings, causing inconsistent performance.
  
• Voltage readings out of spec
  The sensor typically operates within a 0.5–4.5V range. Deviations suggest misalignment or internal failure.
  

Adjustment and Calibration Procedure

• Unplug pump solenoids
  This forces the pump to default to mechanical control, allowing baseline sensor testing.
  
• Measure sensor voltage
  Use a multimeter to check output at idle and under load. Adjust the sensor position to achieve target voltage—usually around 2.5V at neutral swash plate.
  
• Fine-tune with live feedback
  Reconnect solenoids and monitor machine response. Adjust incrementally to balance flow and engine load.
  
• Secure sensor mount
  Loose brackets or worn bushings can cause drift. Replace hardware if needed.
  

Common Pitfalls and Misdiagnoses

• Confusing solenoid failure with sensor issues
  Displacement solenoids may fail independently. Always test them separately before blaming the sensor.
  
• Ignoring harness integrity
  Damaged wires or corroded connectors can mimic sensor faults. Inspect and repair as needed.
  
• Over-adjusting voltage
  Excessive voltage can cause overstroking, leading to engine stall or pump damage.
  

Field Anecdote
In rural Alberta, an EX100-2 operator noticed his machine bogging during trenching. After replacing the angle sensor, performance improved slightly but remained inconsistent. A technician discovered that the sensor bracket was bent, causing misalignment. After reshaping the mount and calibrating voltage, the machine returned to full responsiveness. The operator now checks sensor voltage monthly as part of his maintenance routine.
Preventive Measures and Recommendations

• Log voltage readings during scheduled maintenance
  
• Replace sensor every 3,000–4,000 hours or if readings drift
  
• Use dielectric grease on connectors to prevent corrosion
  
• Train operators to recognize early signs of hydraulic lag
  
• Keep a spare sensor and solenoid on hand for field repairs
  

Conclusion
The angle sensor on the Hitachi EX100-2 is a critical component in hydraulic regulation. Proper calibration ensures smooth operation and prevents engine overload. With careful diagnostics and routine checks, operators can maintain peak performance and extend the life of both pump and engine systems.