Terex TL100 Auxiliary Hydraulic Failure and Troubleshooting Strategy

[MikePhua]

The Terex TL100 and Its Hydraulic Architecture
The Terex TL100 compact wheel loader was introduced as part of Terex’s European-engineered loader series, designed for high maneuverability, operator comfort, and versatile attachment use. With an operating weight of approximately 12,000 pounds and a bucket capacity of 1.3 cubic yards, the TL100 is widely used in municipal work, landscaping, and light construction. Its auxiliary hydraulic circuit allows operators to power attachments such as grapples, snow blowers, augers, and brooms—making it a multi-role machine in tight urban or jobsite environments.
The TL100 features a load-sensing hydraulic system with a variable displacement pump, delivering up to 21 gallons per minute at pressures exceeding 3,000 psi. The auxiliary hydraulics are controlled via an electric solenoid valve, activated by a switch or joystick button in the cab. When this system fails, attachments become inoperable, severely limiting the machine’s utility.
Symptoms of Auxiliary Hydraulic Loss
Operators may encounter the following signs:

• No hydraulic flow to attachment despite engine running
  
• Audible click from solenoid but no pressure buildup
  
• Hydraulic couplers remain dry or inactive
  
• Attachment motor spins weakly or not at all
  
• No change in engine load when activating auxiliary function
  

In one case, a TL100 used for snow removal lost broom rotation mid-shift. The operator heard the solenoid engage but saw no movement. After checking couplers and fluid levels, the issue was traced to a failed solenoid coil.
Core Components of the Auxiliary Circuit
The auxiliary hydraulic system includes:

• Variable displacement pump
  
• Solenoid-operated diverter valve
  
• Hydraulic couplers (flat-face or ISO)
  
• Electrical switch or joystick button
  
• Pressure relief valve
  
• Return line to reservoir
  

The solenoid valve is the gatekeeper—it opens to allow flow when energized. If it fails electrically or mechanically, the circuit remains closed. The couplers must also be fully seated; partial engagement can block flow or cause internal leakage.
Diagnostic Approach and Isolation Techniques
To troubleshoot the loss of auxiliary hydraulics:

• Verify hydraulic fluid level and condition
  
• Inspect couplers for debris or damage
  
• Listen for solenoid engagement when switch is activated
  
• Use a multimeter to check voltage at the solenoid coil
  
• Test continuity across the coil terminals
  
• Manually energize the solenoid with a 12V source
  
• Check for flow at the coupler using a pressure gauge or flow meter
  

If the solenoid clicks but no flow occurs, the valve may be stuck or the coil may be weak. If no click is heard, the issue may be electrical—such as a blown fuse, broken wire, or faulty switch.
Common Failure Points and Field Solutions
Frequent causes of auxiliary hydraulic failure include:

• Solenoid coil burnout due to overheating or voltage spikes
  
• Debris in the valve body preventing spool movement
  
• Worn coupler seals causing internal bypass
  
• Broken switch or relay in the cab
  
• Corroded connectors or damaged harness
  

Solutions include:

• Replacing the solenoid coil with OEM-rated part
  
• Cleaning or rebuilding the valve body
  
• Installing new couplers with fresh seals
  
• Testing and replacing the switch or relay
  
• Applying dielectric grease to connectors and securing harness routing
  

One technician in Ontario found that a TL100’s auxiliary circuit failed due to a pinched wire under the seat. After rerouting and insulating the harness, the system returned to full function.
Preventive Maintenance and System Longevity
To avoid future failures:

• Flush hydraulic fluid annually and replace filters
  
• Grease couplers and inspect for wear monthly
  
• Test solenoid response during pre-shift checks
  
• Avoid prolonged activation without load
  
• Shield wiring from abrasion and moisture
  

A fleet manager in Colorado implemented a quarterly electrical inspection protocol and reduced auxiliary failures by 80%. His team used voltage logs and thermal imaging to detect weak coils before they failed.
Stories from the Field
An operator in Finland shared a story of losing broom rotation during a snowstorm. After checking the fuse and switch, he discovered the solenoid coil had cracked due to thermal cycling. Replacing it with a higher-grade coil restored operation, and he later added a heat shield to prevent recurrence.
Another contractor in New Zealand retrofitted his TL100 with a manual bypass valve for emergency use. When the solenoid failed during a trenching job, he switched to manual mode and completed the task without delay.
Conclusion
Auxiliary hydraulic failure in the Terex TL100 is often caused by solenoid or electrical issues, but can also stem from coupler wear or valve contamination. With a structured diagnostic approach and preventive maintenance, operators can restore function quickly and avoid costly downtime. In a machine built for versatility, keeping the auxiliary circuit healthy ensures the TL100 delivers on every job—from snow to soil, and everything in between.