Troubleshooting Auxiliary Hydraulic Control on Case TR320 Skid Steer

[MikePhua]

The Case TR320 and Its Control System Design
The Case TR320 is a compact track loader introduced in the early 2010s as part of Case Construction’s 300 Series. Designed for versatility in grading, material handling, and attachment work, the TR320 features a vertical lift path, standard-flow hydraulics, and electro-hydraulic joystick controls. Case, founded in 1842 and now part of CNH Industrial, has long emphasized operator comfort and intuitive control systems in its compact equipment.
One of the key features of the TR320 is its proportional auxiliary hydraulic control, typically operated via a roller switch on the right joystick. This switch allows the operator to control hydraulic flow to attachments like grapples, augers, and trenchers. However, when the switch malfunctions or is misconfigured, attachments may only operate in one direction—or not at all.
Symptoms of One-Way Hydraulic Operation
A common issue arises when an attachment with a single hydraulic cylinder, such as a grapple, only closes but won’t open. The roller switch on the right joystick appears to function in one direction, but when rolled the opposite way, there’s no response—no sound, no movement, no pressure.
This behavior suggests a fault in the switch wiring, the control logic, or the hydraulic solenoid itself. In some cases, the switch may physically function but fail to send a signal due to internal wear or incorrect wiring.
Three-Wire vs Six-Wire Switches and Their Implications
One critical detail is the number of wires connected to the roller switch. Some switches have three wires, while others have six. A three-wire switch typically supports single-direction flow, sending a momentary signal when activated. A six-wire switch, on the other hand, can support bi-directional control, allowing the operator to open and close attachments with precision.
If your TR320 is equipped with a three-wire switch, it may be limited to one-way operation unless upgraded. This limitation is especially problematic for attachments that require full hydraulic cycling, such as backhoes or dual-cylinder grapples.
To verify switch type:

• Remove the joystick cover and inspect the wire harness
  
• Count the number of wires leading to the roller switch
  
• Check for unused connectors or pins that may indicate upgrade potential
  
• Consult the wiring diagram in the service manual for signal mapping
  

Testing the Switch and Solenoid Response
Before replacing components, perform a basic test:

• Activate the roller switch in both directions while listening for solenoid clicks
  
• Use a multimeter to check voltage at the switch terminals during activation
  
• Inspect the hydraulic couplers and lines for blockage or pressure imbalance
  
• Swap the attachment hoses to reverse flow and test if the issue follows the circuit
  

If the solenoid clicks in one direction but not the other, the issue likely lies in the switch or wiring. If neither direction activates the solenoid, the problem may be upstream—such as a blown fuse, faulty relay, or controller fault.
Field Anecdotes and Operator Wisdom
One operator in Texas recalled troubleshooting a similar issue on a Case SR130. Initially believing the switch was off-center and only momentary in one direction, he later confirmed that the rocker switch was fully bi-directional. The confusion stemmed from inconsistent response due to a worn contact inside the joystick.
Another technician shared that he replaced a three-wire switch with a six-wire version sourced from a newer model. After updating the harness and reprogramming the controller, the machine gained full auxiliary control—saving hours of manual grapple resets.
Recommendations for Repair and Upgrade
To restore full auxiliary hydraulic function:

• Confirm switch type and wiring configuration
  
• Replace worn or limited switches with OEM bi-directional units
  
• Test solenoid response and inspect hydraulic lines for restriction
  
• Upgrade controller firmware if required for new switch compatibility
  
• Label joystick functions clearly for operator reference
  
• Keep spare switches and relays in the service kit for field repairs
  

For machines used heavily with hydraulic attachments, consider installing a dedicated auxiliary control panel with toggle switches or foot pedals. This reduces wear on joystick components and improves ergonomics.
Conclusion
The Case TR320 is a capable and versatile machine, but its auxiliary hydraulic control system depends on precise switch function and wiring integrity. When attachments only operate in one direction, the issue often lies in the roller switch configuration or signal path. By understanding the difference between three-wire and six-wire setups, testing solenoid response, and upgrading components where needed, operators can restore full functionality and keep their machines working efficiently. In the world of compact loaders, control is everything—and sometimes, it starts with a single wire.