Hydraulic Pressure Switch Failures in Geith Quick Coupler Systems

[MikePhua]

Geith’s Coupler Technology and Its Role in Excavator Safety
Geith, a subsidiary of Doosan Bobcat, has been manufacturing excavator attachments and quick coupler systems for over 60 years. Known for their robust design and safety features, Geith hydraulic couplers allow operators to change buckets and tools without leaving the cab. These systems rely on a combination of hydraulic pressure, mechanical locks, and electronic sensors to ensure secure attachment and safe operation.
One critical component in this system is the pressure switch, which monitors hydraulic flow and signals whether the coupler is locked or unlocked. When functioning properly, it provides real-time feedback to the operator and prevents accidental tool release. However, pressure switch failures have become a recurring issue in some field applications, leading to operational delays and safety concerns.
Terminology Notes

• Pressure Switch: A sensor that detects hydraulic pressure and sends an electrical signal to the control system.
  
• Quick Coupler: A device mounted on the excavator stick that allows rapid attachment changes.
  
• Fail-Safe Mode: A system state that defaults to locked or disabled when sensor input is lost or invalid.
  
• Solenoid Valve: An electrically actuated valve that directs hydraulic flow to lock or unlock the coupler.
  

Symptoms and Operational Impact
Pressure switch failures typically present as:

• False lock/unlock signals on the operator display
  
• Inability to engage or disengage attachments
  
• Unexpected activation of fail-safe mode
  
• Warning lights or audible alarms during operation
  
• Delayed hydraulic response or intermittent control
  

In one documented case, a demolition crew in Ohio experienced repeated coupler lockouts on a 25-ton excavator. The pressure switch intermittently failed to detect hydraulic pressure, triggering the safety override and disabling attachment changes mid-cycle. After replacing the switch twice, they discovered that vibration and heat exposure had degraded the internal contacts.
Field Anecdote and Improvisation
During a sewer line installation in Alberta, a contractor faced a pressure switch failure on a Geith coupler while trenching. With no replacement part available, the operator bypassed the switch temporarily by manually locking the coupler and disabling the sensor input. The machine continued operating safely under strict visual checks until the correct switch was installed three days later. The incident prompted the company to stock spare switches and add a vibration-dampening bracket to future installations.
Root Causes and Diagnostic Strategy
Pressure switch failures often stem from:

• Internal corrosion due to moisture ingress
  
• Vibration-induced contact fatigue
  
• Overheating from proximity to hydraulic lines
  
• Electrical connector wear or pin misalignment
  
• Incorrect installation torque causing seal failure
  

To diagnose:

• Check voltage output from the switch under pressure
  
• Inspect connector pins for corrosion or looseness
  
• Test continuity across switch terminals with and without hydraulic flow
  
• Verify mounting orientation and torque against manufacturer specs
  
• Monitor switch behavior during warm-up and extended operation
  

If the switch fails intermittently, thermal cycling or vibration is likely the culprit. If it fails consistently, internal damage or connector failure is more probable.
Preventive Maintenance and Recommendations

• Replace pressure switches every 2,000 hours or when symptoms appear
  
• Use sealed connectors and dielectric grease to prevent corrosion
  
• Install vibration isolators or brackets to reduce mechanical stress
  
• Shield switches from direct heat exposure using thermal wraps
  
• Perform sensor calibration during routine service intervals
  
• Keep spare switches and solenoids in fleet inventory
  

For machines operating in extreme environments, consider upgrading to ruggedized switches rated for high vibration and temperature.
Design Simplicity and Serviceability
Geith coupler systems are designed for field serviceability. Pressure switches are externally mounted and accessible without removing major components. The hydraulic circuit includes diagnostic ports, and the electrical system uses modular connectors for quick replacement. Operators can manually verify coupler engagement using visual indicators and mechanical locks, even when sensors fail.
While newer models include CAN bus integration and digital diagnostics, the core system remains mechanically intuitive, making it suitable for mixed fleets and remote operations.
Conclusion
Pressure switch failures in Geith hydraulic coupler systems are a manageable but disruptive issue. With proper diagnostics, preventive care, and thoughtful installation, operators can maintain safe and efficient attachment changes. In excavator operations, connection integrity is non-negotiable—and the pressure switch, though small, plays a critical role in keeping tools secure and productivity flowing.