Hanna Control Box Troubleshooting in the Champion 68-12F Grader

[MikePhua]

The Champion 68-12F and Its Mechanical Legacy
The Champion 68-12F motor grader was part of a long-standing lineage of road construction equipment developed by Champion Road Machinery, a Canadian company founded in the early 20th century and later acquired by Volvo Construction Equipment. The 68-12F was introduced in the late 1980s and became widely used for municipal road maintenance, forestry access grading, and rural infrastructure development.
With an operating weight of approximately 30,000 pounds and a Cummins-powered drivetrain, the 68-12F offered a balance of mechanical simplicity and hydraulic sophistication. Its blade control system, powered by electro-hydraulic actuators and governed by the Hanna control box, allowed precise articulation of the moldboard, circle, and lift arms—critical for fine grading and slope shaping.
Understanding the Hanna Control Box
The Hanna control box is an electro-hydraulic interface that translates operator inputs into proportional valve movements. It typically includes toggle switches, potentiometers, and relays that send signals to solenoids mounted on the hydraulic valve bank. These solenoids then modulate fluid flow to cylinders controlling blade lift, tilt, side shift, and articulation.
Key components of the Hanna system include:

• Toggle switches for directional control
  
• Potentiometers for speed modulation
  
• Relays for signal amplification
  
• Fuses and circuit breakers for protection
  
• Wiring harnesses connecting to solenoids
  

The system is designed to be intuitive, but over time, electrical degradation, corrosion, and mechanical wear can lead to erratic behavior or complete failure of blade functions.
Common Symptoms and Failure Modes
Operators may encounter issues such as:

• Blade functions responding intermittently or not at all
  
• Toggle switches failing to activate solenoids
  
• Audible clicking from relays without hydraulic response
  
• Burnt fuses or melted wires inside the control box
  
• Solenoids heating excessively or failing to energize
  

In one case, a grader lost left lift and side shift control while the rest of the blade functions remained operational. Inspection revealed a failed relay and a corroded ground wire inside the Hanna box. After replacing the relay and cleaning the terminals, full functionality was restored.
Diagnostic Approach and Isolation Techniques
Troubleshooting the Hanna control box requires a methodical approach:

• Begin with a visual inspection of all wires, connectors, and terminals
  
• Use a multimeter to check voltage at each switch and solenoid
  
• Test continuity across relays and potentiometers
  
• Verify fuse integrity and amperage ratings
  
• Check ground connections for corrosion or looseness
  
• Activate each switch while monitoring solenoid response
  

If a specific function fails, isolate the circuit by bypassing the switch and energizing the solenoid directly. If the solenoid responds, the fault lies in the control box. If not, the issue may be hydraulic or mechanical.
Solenoid and Valve Bank Considerations
The hydraulic valve bank on the 68-12F includes multiple solenoids, each controlling a specific blade function. These solenoids are typically 12V or 24V DC and require clean, uninterrupted power to operate. Over time, they may suffer from:

• Coil burnout due to overvoltage or heat
  
• Plunger sticking from contamination
  
• Connector corrosion from moisture ingress
  
• Internal short circuits
  

To test a solenoid:

• Disconnect the wire and apply direct voltage from a battery
  
• Listen for a click indicating actuation
  
• Measure resistance across terminals (typical range: 10–40 ohms)
  
• Inspect for heat damage or melted insulation
  

If a solenoid fails, replace it with an OEM or high-quality aftermarket unit rated for the same voltage and flow characteristics.
Control Box Rebuild and Upgrade Options
If the Hanna control box is severely damaged or obsolete, rebuilding or upgrading may be necessary. Options include:

• Replacing toggle switches and relays with modern equivalents
  
• Installing sealed connectors and weatherproof housings
  
• Upgrading to a programmable logic controller (PLC) for enhanced diagnostics
  
• Retrofitting with joystick controls and proportional valves
  

Some operators choose to bypass the Hanna system entirely and install manual hydraulic levers, especially in remote regions where electronic parts are hard to source. While this reduces precision, it increases reliability and ease of repair.
Preventive Maintenance and Electrical Reliability
To extend the life of the Hanna control system:

• Inspect and clean connectors monthly
  
• Apply dielectric grease to terminals
  
• Replace fuses with correct amperage ratings
  
• Shield the control box from moisture and vibration
  
• Label wires and maintain a wiring diagram for reference
  

A fleet manager in Saskatchewan implemented a quarterly electrical inspection protocol and reduced grader downtime by 50% over two years. His team used color-coded tags and documented voltage readings for each function.
Stories from the Field
One operator in Montana shared a story of his 68-12F losing blade tilt during a snow removal job. After tracing the fault to a broken toggle switch inside the Hanna box, he replaced it with a salvaged switch from a combine harvester. The grader returned to service within an hour, highlighting the value of cross-equipment parts knowledge.
Another technician in New South Wales rebuilt an entire Hanna box using marine-grade switches and relays. His grader now operates in coastal conditions with zero electrical faults after 18 months of service.
Conclusion
The Hanna control box in the Champion 68-12F grader is a vital link between operator input and hydraulic precision. While aging components and environmental exposure can cause failures, methodical diagnostics and targeted repairs can restore full functionality. Whether rebuilding the box, upgrading the system, or retrofitting manual controls, understanding the interplay between electronics and hydraulics ensures reliable grading performance in any terrain.