Intermittent Shutdown in the Takeuchi TB135 Excavator

[MikePhua]

The TB135 and Its Compact Excavator Legacy
The Takeuchi TB135 compact excavator was introduced in the early 2000s as part of Takeuchi’s expansion into the 3–4 ton class. Designed for urban construction, landscaping, and utility trenching, the TB135 featured a 28.4 kW Yanmar diesel engine, pilot-operated hydraulics, and a zero-tail swing profile. Its reputation for reliability and ease of maintenance made it a popular choice among rental fleets and owner-operators. By 2010, Takeuchi had sold thousands of units across North America, with strong adoption in the southeastern United States.
Despite its mechanical simplicity, the TB135 incorporated electronic control modules and relay-based safety systems that, over time, became known for intermittent faults—especially in machines exposed to vibration, moisture, and electrical fatigue.
Symptoms of the Shutdown Issue
A recurring issue with the TB135 involves the engine running smoothly for 10–15 minutes before abruptly shutting down. After a brief cooldown period, the engine restarts and repeats the cycle. Operators report:

• No overheating indicators
  
• Normal oil pressure (typically 60 psi)
  
• Fuel delivery appears uninterrupted
  
• Shutdown resembles a switch-off rather than a gradual stall
  

This behavior suggests an electrical fault rather than a mechanical or fuel-related issue. The most likely culprit is the machine’s controller activating an emergency idle or shutdown relay due to a false signal or internal failure.
Controller Location and Access Challenges
The TB135’s controller is mounted beneath the left joystick, behind the fuse panel. Accessing it requires tilting the operator platform or removing side panels. The relays and circuit boards are housed in a compact enclosure, often obscured by wiring harnesses and hydraulic lines.
Operators attempting to inspect the controller should:

• Disconnect the battery before accessing electrical components
  
• Use a flashlight and mirror to locate the relay cluster
  
• Label wires before disconnecting to avoid misrouting
  
• Check for signs of corrosion, loose connectors, or burnt solder joints
  

Triple Relay Failure and Cold Solder Joints
One of the most common electrical failures in the TB135 involves the triple relay modules—specifically the #9 relay, which controls emergency idle and shutdown functions. These relays are prone to cold solder joints, where poor bonding between the relay pin and circuit board causes intermittent contact.
Symptoms of relay failure include:

• Sudden engine shutdown without warning
  
• Detent lights flickering or staying on
  
• Inconsistent response from hydraulic lockout switches
  

Rather than replacing the relay outright, technicians often resolder the joints using a fine-tip soldering iron and flux. This restores conductivity and prevents future failures. However, all relays in the cluster should be inspected, as poor soldering is a systemic issue in this model.
Fuel System and Water Separator Inspection
If the engine stalls gradually rather than shutting off instantly, the issue may lie in the fuel system. The TB135 uses a water separator assembly with an inlet tube that can become clogged with debris. Operators should:

• Remove the separator and inspect the inlet tube
  
• Run a flexible wire through the tube to verify flow
  
• Check the tank outlet for sediment or blockage
  
• Replace fuel filters and bleed the system
  

In one documented case, a TB135 in Pennsylvania exhibited similar symptoms due to a plugged separator inlet. After cleaning the tube and flushing the tank, the engine ran continuously without issue.
Platform Tilt and Maintenance Access
The TB135’s operator platform is designed to tilt upward for service access. If access covers are seized or corroded, technicians can:

• Apply penetrating oil to hinge points
  
• Use a pry bar with caution to avoid damaging mounts
  
• Replace worn gas struts or locking pins
  
• Clean debris from pivot areas to restore movement
  

Routine maintenance is simplified when the platform tilts properly, allowing full access to relays, fuses, and hydraulic valves.
A Story from Coastal North Carolina
An operator in Wilmington experienced repeated shutdowns on his TB135 while trenching for irrigation lines. After replacing fuel filters and inspecting the tank, the issue persisted. He eventually traced the fault to a cracked solder joint on the #9 relay. Using a magnifying glass and soldering kit, he repaired the joint and restored full function. The machine ran flawlessly for the remainder of the season, and he later resoldered all relays as a preventative measure.
Conclusion
Intermittent shutdowns in the Takeuchi TB135 are often electrical in origin, with triple relay modules and controller logic being the primary suspects. While fuel system issues can mimic similar symptoms, the abrupt nature of the shutdown typically points to relay failure. With careful inspection, soldering repairs, and attention to access points, operators can restore reliability and extend the life of this compact workhorse—proving that even small machines demand precision when it comes to diagnostics.