Restoring Auxiliary Hydraulic Function on a Bobcat T190

[MikePhua]

The Bobcat T190 and Its Hydraulic Architecture
The Bobcat T190 compact track loader was introduced in the early 2000s as part of Bobcat’s push into mid-sized tracked machines. With an operating weight of approximately 7,600 pounds and a rated operating capacity of 1,900 pounds, the T190 became a popular choice for contractors, landscapers, and municipalities. It featured a standard hydraulic system with optional high-flow capability, allowing for a wide range of attachments including augers, grapples, and tilt-tach systems.
Bobcat, founded in North Dakota in the 1950s, revolutionized compact equipment with its skid-steer loaders. By the time the T190 was released, Bobcat had sold hundreds of thousands of machines globally, and the T190 quickly became one of its best-selling track loaders due to its balance of power, maneuverability, and attachment versatility.
Symptoms of Auxiliary Hydraulic Failure
A common issue reported by operators is the sudden failure of the auxiliary hydraulic system to engage. In one case, a 2002 T190 with standard hydraulics failed to activate the auxiliary circuit when connected to a tilt-tach attachment. The left panel light did not illuminate, and the right joystick controls were unresponsive. However, during startup, the auxiliary light briefly flashed, indicating that the bulb and circuit were not entirely dead.
This type of failure typically presents with:

• No response from auxiliary controls
  
• Indicator light not staying on
  
• All other machine functions operating normally
  
• No visible wiring damage or blown fuses
  

These symptoms suggest an electrical or control logic fault rather than a mechanical or hydraulic failure.
Electrical and Control Panel Diagnostics
The T190 uses a centralized control panel to manage auxiliary hydraulic activation. The left panel switch sends a signal to the controller, which then energizes the solenoid controlling hydraulic flow to the auxiliary circuit. If the switch fails, the controller doesn’t receive the signal, and the system remains inactive.
Key diagnostic steps include:

• Inspecting the fuse panel for blown fuses (even if they visually appear intact, test with a multimeter)
  
• Re-seating connectors, especially the main cabinet harness and the left panel connector
  
• Checking for corrosion or loose pins in connector #408, which links the control panel to the hydraulic logic
  
• Verifying that the switch itself is functional using continuity testing
  

In some cases, the switch panel may be physically stuck or difficult to open due to age and environmental exposure. Forcing it open risks cracking the plastic, so applying gentle heat or using plastic trim tools may help.
Mouse Damage and Wiring Integrity
Rodent damage is a frequent culprit in machines stored outdoors or in barns. Mice often chew through wiring insulation, causing intermittent faults. While no damage was found in this case, it’s worth inspecting:

• Behind the engine compartment
  
• Under the operator seat
  
• Around the fuse box and relay cluster
  
• Near the hydraulic valve block
  

Use a flashlight and mirror to inspect hard-to-reach areas. Look for frayed wires, nesting material, or chewed insulation.
Control Module and Software Logic
If all physical components check out, the issue may lie in the control module itself. The Bobcat controller uses software logic to manage hydraulic functions, and a fault or glitch can prevent activation. Power cycling the machine may temporarily reset the logic, but if the fault persists, a diagnostic scan tool may be required to read error codes and verify module health.
Some operators report success by disconnecting the battery for several minutes to force a full reset of the control system. Others have replaced the switch panel entirely when internal contacts failed due to oxidation.
Field Anecdotes and Practical Solutions
A retired mechanical engineer in Delaware encountered this exact issue and methodically tested each component. After confirming fuse integrity and connector seating, he suspected the switch panel itself. While unable to open it without risking damage, he noted that the auxiliary light flashed during startup—suggesting the panel was receiving power but not sending the activation signal.
In similar cases, operators have bypassed the panel switch using a direct toggle wired to the solenoid, restoring auxiliary function temporarily. However, this approach should be used with caution and only as a diagnostic tool, not a permanent fix.
Preventative Measures and Long-Term Recommendations
To avoid future failures:

• Periodically clean and inspect electrical connectors with dielectric grease
  
• Store machines indoors or use rodent deterrents in engine compartments
  
• Replace aging switch panels before they fail completely
  
• Use a diagnostic scan tool to monitor controller health and error codes
  
• Label and document all connector locations during service for easier troubleshooting
  

If the auxiliary system is critical to daily operations, consider upgrading to a newer control panel or installing a redundant activation circuit with proper safety interlocks.
Conclusion
Auxiliary hydraulic failure on a Bobcat T190 is often rooted in electrical or control logic issues rather than hydraulic malfunction. By methodically inspecting fuses, connectors, switches, and wiring, operators can isolate the fault and restore functionality. With proper maintenance and attention to environmental risks, the T190’s hydraulic system can continue powering attachments reliably for years to come.