Telsta A-28D Emergency Lower Solenoid: Location, Wiring, and Troubleshooting

[MikePhua]

For operators and technicians working with the Telsta A-28D aerial lift, understanding the emergency lower solenoid's role, its location, and associated wiring is crucial for safe and efficient operation. This guide delves into these aspects, providing insights into the solenoid's function, common issues, and maintenance practices.
Understanding the Emergency Lower Solenoid
The emergency lower solenoid is an integral component of the Telsta A-28D's hydraulic system. It is a solenoid-operated valve located on the lift cylinder. When activated, this valve allows hydraulic oil to bleed off from the base of the lift cylinder, enabling the boom to lower manually in the event of a hydraulic system failure or power loss. This feature ensures that the boom can be safely lowered to the ground, preventing potential hazards associated with an elevated, unsupported boom.
Location of the Emergency Lower Solenoid
The emergency lower solenoid is typically situated on the lift cylinder assembly. To access it:

1. Position the Boom: Ensure the boom is elevated to a safe angle, typically around 45 degrees, to provide adequate clearance.
   
2. Secure the Boom: Use an overhead hoist or jack with a minimum one-ton rated capacity to support the boom. This step is critical to prevent the boom from dropping unexpectedly during maintenance.
   
3. Access the Solenoid: Depending on the model and configuration, the solenoid may be located near the base of the lift cylinder. In some cases, it might be necessary to remove surrounding components or panels to gain clear access.
   

Wiring Diagram and Electrical Connections
The emergency lower solenoid is electrically connected to the control system, allowing operators to activate it from the basket. The wiring typically includes:

• Power Supply: A wire from the control panel or basket switch provides power to the solenoid.
  
• Ground Connection: A grounding wire ensures proper electrical return.
  
• Activation Signal: A signal wire from the control switch or relay activates the solenoid.
  

For precise wiring diagrams, refer to the Telsta A-28D service manual, which provides detailed schematics specific to the model.
Common Issues and Troubleshooting
Operators may encounter several issues related to the emergency lower solenoid:

• Boom Drifting Down: If the boom drifts down slowly, it may indicate a faulty holding valve or emergency lower valve. In such cases, inspect the solenoid and associated components for wear or damage.
  
• Boom Not Lowering: If the boom does not lower when the emergency lower solenoid is activated, check for electrical issues such as a blown fuse, faulty relay, or damaged wiring.
  
• Hydraulic Leaks: Leaks around the solenoid area can result from worn O-rings or seals. Regular inspection and replacement of these components can prevent such issues.
  

Maintenance Tips
To ensure the emergency lower solenoid functions correctly:

• Regular Inspection: Periodically check the solenoid and surrounding components for signs of wear, corrosion, or damage.
  
• Clean Connections: Ensure all electrical connections are clean and free from corrosion to maintain proper function.
  
• Replace Worn Components: Promptly replace any worn or damaged O-rings, seals, or electrical components to prevent system failures.
  

Real-World Example
An operator shared their experience with a similar model:

"I had to replace the dipper on my 1972 JD 310. After soaking the pins overnight with penetrating oil, I was able to remove them using a hammer and punch. The dipper came off without any issues, but I had a helper to support the weight."

This highlights the importance of preparation and assistance when dealing with heavy components.
Conclusion
Understanding the emergency lower solenoid's location, wiring, and maintenance is essential for the safe operation of the Telsta A-28D aerial lift. Regular inspections and prompt attention to issues can ensure the system remains functional, providing operators with the confidence to perform their tasks safely and efficiently.