Diagnosing and Resolving Control Reversal in the Bobcat T190 Skid Steer

[MikePhua]

Introduction to Control Systems in the T190
The Bobcat T190 skid steer is equipped with selectable control patterns—primarily ISO and H-pattern—allowing operators to choose their preferred joystick configuration. These systems are governed by an electronic controller that interprets joystick input and translates it into hydraulic movement. When control behavior becomes erratic or reversed, it often points to issues in the control pattern selection system, electrical faults, or miscommunication between the operator and machine setup.
Terminology Clarified

• ISO Pattern: Standard control layout where the left joystick controls drive (forward/reverse/turn) and the right joystick controls lift and tilt.
  
• H-Pattern: Both joysticks control drive and loader functions in a split configuration.
  
• ACS (Advanced Control System): Bobcat’s system that allows switching between control patterns electronically.
  
• TSB (Technical Service Bulletin): Manufacturer-issued advisory for known issues and recommended fixes.
  
• Fuse 11: A critical fuse in the T190’s electrical system that powers the control selector switch.
  

Common Symptoms of Control Reversal
Operators may report that pushing both joysticks forward causes the machine to drive backward, or that the loader functions behave unpredictably. These symptoms typically arise after maintenance, such as drive motor replacement, or when the machine has been transported and restarted under different conditions.
Step-by-Step Diagnostic Approach

• Verify Control Pattern Selection
  Ensure the machine is set to the correct control pattern. The default is ISO. If the operator unknowingly switches to H-pattern, control behavior will differ significantly.
  
• Inspect Fuse 11 and Selector Switch
  Check for power at Fuse 11 and continuity through the selector switch. A missing 12V signal to the controller can prevent pattern switching.
  
• Test Parking Brake Release
  In H-pattern mode, the parking brake may not release if the system doesn’t receive the correct signal. This can be misinterpreted as a control fault.
  
• Check for TSBs
  Bobcat has issued service bulletins addressing control pattern malfunctions. These may include software updates or wiring harness inspections.
  

Field Anecdote: The Raleigh Reversal
A technician in Raleigh, NC, repaired a drive motor on a T190 and returned it to the shop. The operator later reported reversed controls. Upon inspection, the technician found the machine had been inadvertently switched to H-pattern, and the parking brake wouldn’t release due to a missing signal. After checking Fuse 11 and resetting the selector, the machine returned to normal operation. This case underscores the importance of verifying control settings post-repair.
Best Practices for Preventing Control Confusion

• Label Control Pattern Selector Clearly
  Use decals or tags to indicate ISO vs. H-pattern positions.
  
• Educate Operators
  Provide training on control pattern differences and how to switch modes safely.
  
• Post-Maintenance Checklist
  After any repair involving drive motors or electrical systems, verify control behavior before releasing the machine.
  
• Document Settings
  Record control pattern and fuse status during service to aid future diagnostics.
  

Historical Context: Evolution of Skid Steer Controls
Early skid steers used mechanical levers and foot pedals. As joystick systems emerged in the 1990s, manufacturers introduced selectable control patterns to accommodate operator preferences. Bobcat’s ACS system was a leap forward, allowing seamless switching between ISO and H-pattern. However, this flexibility introduced new diagnostic challenges, especially when electrical faults mimic mechanical issues.
Case Study: Fleet Troubleshooting in Wisconsin
A contractor in Wisconsin reported inconsistent control behavior across a fleet of T190s. After a systematic inspection, technicians found that several machines had faulty selector switches and blown fuses. By standardizing control settings and replacing worn components, the fleet regained uniform performance. The contractor noted a 15% reduction in operator error incidents post-adjustment.
News Spotlight: Push for Universal Control Standards
In 2024, industry groups proposed a universal control pattern standard for skid steers to reduce training time and improve safety. While manufacturers like Bobcat support flexibility, the initiative sparked debate over operator autonomy versus standardization. The proposal remains under review, but it highlights the growing importance of intuitive machine interfaces.
Conclusion
Control reversal in the Bobcat T190 is often a symptom of misconfigured settings or minor electrical faults. By understanding the ACS system, verifying fuse integrity, and educating operators, technicians can swiftly resolve these issues. The T190’s adaptability is a strength—but only when paired with clear procedures and informed users.