Troubleshooting the Bobcat 753F BOSS System: A Comprehensive Guide

[MikePhua]

The Bobcat 753F Skid-Steer Loader, particularly models equipped with the BOSS (Bobcat Onboard Safety System), is renowned for its versatility and reliability in various construction and landscaping tasks. However, like any complex machinery, the BOSS system can encounter issues that may hinder its performance. Understanding the components, common problems, and effective troubleshooting steps is essential for maintaining optimal functionality.
Understanding the BOSS System
The BOSS system in the Bobcat 753F serves as an integrated monitoring and safety feature, providing real-time data on engine and hydraulic temperatures, pressures, and other critical parameters. It also includes an onboard diagnostic function that alerts operators to potential issues, ensuring timely maintenance and preventing damage to the machine.
Common Issues with the BOSS System

1. Non-Responsive or Blank Display
   A frequently reported issue is the BOSS display failing to show any readings, remaining blank or displaying only dashes. This could be due to:
   • Blown Fuse: The BOSS system relies on specific fuses; a blown fuse can disrupt its operation.
     
   • Faulty BOSS Controller: The controller, located under the cab behind the operator's left shoulder, might be malfunctioning.
     
   • Corroded Connectors: Multi-wire connectors on the BOSS controller can corrode over time, leading to poor connections.
     
   • Grounding Issues: Multiple ground connections near the BOSS controller may become loose or corroded, affecting system performance.
     
2. Erratic or Inaccurate Readings
   Sometimes, the display shows incorrect data, such as constant low readings or fluctuating values. Potential causes include:
   • Faulty Sensors: Temperature or pressure sensors may be damaged or miscalibrated.
     
   • Wiring Issues: Damaged or frayed wires can lead to signal interference.
     
   • Controller Malfunction: The BOSS controller itself might be failing to process data correctly.
     
3. System Shutdowns
   In some cases, the loader operates briefly before shutting down, often accompanied by an error code. This is typically a safety feature activated by the BOSS system when it detects abnormal readings, such as:
   • Overheating: Excessive engine or hydraulic temperatures.
     
   • Low Hydraulic Pressure: Indicating potential pump or valve issues.
     
   • Sensor Failures: Malfunctioning sensors that provide incorrect data to the system.
     

Troubleshooting Steps
To diagnose and resolve BOSS system issues, follow these steps:

1. Inspect Fuses
   Check the BOSS fuse in the fuse block. A blown fuse can prevent the system from operating correctly.
   
2. Examine the BOSS Controller
   Raise the cab and locate the BOSS controller. Ensure it is securely mounted and hasn't been removed or tampered with.
   
3. Check Connectors and Wiring
   Inspect all multi-wire connectors on the BOSS controller for signs of corrosion or loose connections. Clean or replace as necessary.
   
4. Verify Ground Connections
   Locate and clean all ground connections near the BOSS controller. Ensure they are free of corrosion and securely attached.
   
5. Test Sensor Resistances
   Using a multimeter, measure the resistance of the temperature and pressure sensors. Compare the readings with the specifications in the service manual.
   
6. Check Voltage at the Display
   Measure the voltage at the display's connector pins:
   • Pin A: Should have approximately 5V.
     
   • Pin E: Should have 12V for the backlight.
     
   • Black Wire: Ground.
     
   • Purple Wires: Data lines from the controller.
     
7. Use Diagnostic Tools
   If available, use the BOSS diagnostic tool to check for error codes and verify communication between the controller and display.
   

Potential Solutions

• Replace Faulty Components: If a specific sensor or the BOSS controller is identified as faulty, replace it with OEM parts.
  
• Bypass the BOSS System: In cases where replacement parts are unavailable, consider installing a Push-To-Operate conversion kit to bypass the BOSS system. This allows the loader to operate without the safety monitoring features.
  
• Manual Override: For immediate operation, manually open the engine shutoff solenoid and secure it in the open position. This can be achieved by wedging it open temporarily, allowing the engine to run without BOSS intervention.
  

Preventive Measures
To prevent future BOSS system issues:

• Regular Maintenance: Perform routine inspections and maintenance on the BOSS system components.
  
• Cleanliness: Keep connectors and sensors clean to prevent corrosion and ensure accurate readings.
  
• Proper Storage: Store the loader in a dry, clean environment to minimize exposure to elements that can cause damage.
  

Conclusion
The BOSS system in the Bobcat 753F is a vital component for ensuring the safety and efficiency of the loader. By understanding its functions and common issues, operators can effectively troubleshoot and maintain the system, ensuring prolonged equipment life and optimal performance.