Understanding JLG Wiring Diagrams: The Meaning of Solid Black Triangles and Electrical Symbols

[MikePhua]

Introduction to JLG Wiring Diagrams
JLG aerial work platforms and lifts rely heavily on electrical systems to operate safely and efficiently. Wiring diagrams are essential tools for technicians and operators to diagnose, repair, and maintain these machines. Understanding the symbols used in these diagrams is crucial, especially when deciphering less obvious notations like solid black triangles.
What Solid Black Triangles Represent
In JLG wiring diagrams, solid black triangles commonly denote the direction of current flow or signal path within electrical circuits. These triangles act as visual indicators guiding the technician through the wiring logic, showing how power or signals move from one component to another. Recognizing these symbols helps in tracing circuits systematically during troubleshooting.

• Directional Indicator: The triangle points along the wire or connector path, indicating where electrical current or signals travel.
  
• Signal Flow Clarification: In complex diagrams with multiple branches, triangles prevent confusion by clearly marking intended current directions.
  
• Associated Components: Often appear near switches, relays, sensors, and control modules to illustrate how these parts interact electrically.
  

Common Electrical Symbols in JLG Wiring Diagrams
Beyond solid black triangles, several other standard symbols are frequently used:

• Lines: Represent wires or electrical conductors connecting components.
  
• Switch Symbols: Indicate on/off positions or momentary contact states.
  
• Relays: Shown with coils and switching contacts to represent electromagnetic switching.
  
• Ground Symbols: Denote electrical earth or chassis grounding points.
  
• Fuses and Circuit Breakers: Mark protective devices safeguarding circuits.
  
• Connectors: Circles or blocks indicating plug-in connections between harnesses.
  
• Resistors and Capacitors: Components that modify current flow or store energy, sometimes present in control circuits.
  

How to Read and Interpret These Diagrams

• Follow the Flow: Start at the power source or battery symbol and trace the arrows or directional triangles through switches, relays, and loads.
  
• Identify Components: Use the legend or key to understand each symbol’s meaning.
  
• Check Connections: Note connectors and wire colors to locate actual harness points on the machine.
  
• Look for Ground Points: Confirm proper grounding to avoid electrical faults.
  
• Understand Circuit Protection: Recognize fuses and breakers to troubleshoot open circuits safely.
  

Troubleshooting Using Wiring Diagrams
Understanding these symbols empowers technicians to:

• Quickly locate faults such as broken wires, blown fuses, or stuck relays.
  
• Verify signal flow to sensors and control units.
  
• Diagnose why certain functions, like boom movement or platform controls, fail.
  
• Ensure correct wiring during repairs or modifications.
  

Terminology and Annotations Explained

• Current Flow: The movement of electrical charge through conductors.
  
• Signal Path: The route taken by control or sensor signals within a circuit.
  
• Ground (Earth): Reference point in circuits connected to the vehicle chassis for safety.
  
• Relay: Electromechanical switch activated by electrical signals.
  
• Fuse: Safety device that breaks the circuit if current exceeds a limit.
  
• Connector: Physical interface joining wiring harness sections.
  

Real-World Application and Case Study
A JLG technician repairing a malfunctioning platform control switch relied on wiring diagrams with solid black triangles to trace signal flow from the joystick to the control module. By following the triangles, the technician identified a faulty relay coil that was preventing the signal from reaching the motor controller. Replacing the relay restored full operation, showcasing the practical importance of understanding these diagram symbols.
Summary of Key Points

• Solid black triangles in JLG wiring diagrams indicate current or signal flow direction.
  
• These symbols are crucial for accurately interpreting complex electrical schematics.
  
• Other standard electrical symbols complement these diagrams, representing switches, relays, grounds, and connectors.
  
• Proper reading of wiring diagrams facilitates efficient troubleshooting and repair.
  
• Knowledge of terminology aids communication and documentation during maintenance.
  

Conclusion
Mastering the interpretation of JLG wiring diagrams, particularly the meaning of solid black triangles, is indispensable for anyone involved in the maintenance or repair of aerial work platforms. These symbols provide clarity to complex electrical systems, allowing for precise diagnosis and effective solutions. Through consistent study and practical application, technicians can ensure the reliability and safety of JLG machines in demanding work environments.