Troubleshooting Auxiliary Hydraulics on the John Deere 328D Skid Steer

[MikePhua]

The John Deere 328D is a high-performance skid steer loader used across industries from construction to agriculture. Known for its power, visibility, and joystick control system, it’s a favorite among operators. However, like many advanced machines, its auxiliary hydraulic system can pose challenges when malfunctions arise—especially when attachments rely on consistent, high-pressure flow.
Understanding the Role of Auxiliary Hydraulics
Auxiliary hydraulics are the lifeline for attachments such as hydraulic hammers, augers, brush cutters, and grapple buckets. In the 328D, these hydraulics are controlled by an electro-hydraulic system using solenoids and a switchable control valve. This makes diagnosis more complex than traditional lever-actuated systems but also offers improved responsiveness and integration.
A failure in this system can render attachments inoperable, significantly reducing job efficiency. Troubleshooting requires a systematic approach, starting with the operator controls and extending all the way to the valve body and solenoids.
Common Issues and Diagnostic Path
Some common problems users face include:

• No Hydraulic Flow to the Attachment
  This is often the result of a control circuit issue or an electrically stuck valve. A simple test with a known working attachment can quickly rule out implement-side failure.
  
• Hydraulics Engage But Do Not Lock or Latch
  In many machines like the 328D, pressing the switch only sends temporary signal pulses unless the switch is held or latched electronically. This can be a source of confusion for newer operators. The solution is often found in understanding the logic of the switch—whether it's momentary or latched.
  
• Intermittent Flow or Low Pressure
  Could be caused by a weak solenoid coil, contaminated hydraulic fluid, or partially blocked quick couplers. An operator in Alberta recounted losing attachment flow mid-job, only to find the quick couplers had become slightly disconnected due to vibration. Cleaning and fully re-seating the couplers resolved the issue.
  
• Dashboard Warnings and Fault Codes
  The John Deere 328D is equipped with a diagnostic panel that can display error codes for hydraulic systems. Consulting the service manual or dealer database is critical when these codes appear. As in one documented case, a persistent code indicating "AUX pressure override" turned out to be a bad pressure switch.
  

Electrical vs. Hydraulic: Knowing Where to Look First
Most failures in the auxiliary system are not due to failed pumps or massive leaks—they’re electrical. The 328D relies on a sealed harness system that includes fuses, relays, rocker switches, and solenoids. A single corroded connection can break the circuit, making a multimeter and wiring diagram indispensable tools.
An Illinois-based contractor discovered his hydraulics wouldn’t engage because of a blown 5-amp fuse tied to the auxiliary switch. Replacing it was a $0.50 fix—but cost half a day's downtime due to lack of documentation.
Hydraulic Best Practices for Preventing Problems

• Keep Couplers Clean: Dirt is the #1 enemy. Cap unused ports and clean both sides before connecting.
  
• Regularly Inspect Hoses and Fittings: Look for abrasion, leaks, or swelling.
  
• Use Correct Hydraulic Fluid: Mixing incompatible fluids can degrade seals and cause flow problems.
  
• Train Operators: Knowing how the control system works prevents many operator-induced faults, especially regarding latching mechanisms.
  

Technology as a Double-Edged Sword
As machines like the 328D adopt more sophisticated electronic controls, troubleshooting has shifted from purely mechanical diagnostics to hybrid skills involving both electronics and hydraulics. This evolution mirrors trends across the equipment world—where technology increases efficiency but demands higher technician literacy.
Caterpillar, Case, and Kubota machines have reported similar auxiliary control quirks in their electronically controlled models, often with similar root causes: operator misunderstanding, electrical gremlins, or poor maintenance of coupler integrity.
Conclusion
Auxiliary hydraulic issues on the John Deere 328D can be frustrating, especially when working against tight project deadlines. However, most issues trace back to electrical control systems, basic operator awareness, or simple maintenance oversights. Armed with the right knowledge, service manual, and diagnostic tools, even complex problems can be solved quickly—getting your machine, and your job, back on track.