Troubleshooting Cat 236B Skid Steer Auxiliary Hydraulics Not Working

[MikePhua]

The Caterpillar 236B skid steer loader, a versatile and powerful machine used in various applications such as snow pushing, dirt moving, and brush cutting, occasionally encounters issues with its auxiliary hydraulics. Auxiliary hydraulics are essential for operating attachments like brush cutters, grapples, and augers, and when they fail to function, productivity can be significantly impacted. This article offers a comprehensive, detailed troubleshooting guide and advice for resolving auxiliary hydraulic problems on the Cat 236B.
Symptoms and Initial Checks
Common signs of auxiliary hydraulic failure include attachments not responding despite being properly connected, and the operator being unable to engage flow through joystick controls or auxiliary switches.
First steps in troubleshooting typically involve:

• Checking the auxiliary hydraulic engagement controls, mostly thumbwheels or switches on the left or right joystick.
  
• Inspecting all relevant electrical fuses related to auxiliary hydraulic power and control circuits.
  
• Confirming that hydraulic fluid levels in the reservoir meet specifications.
  

Control Activation and Safety Features
The Cat 236B skid steer employs dual joystick controls equipped with thumbwheels that regulate auxiliary flow rate and direction. Operators should ensure:

• The thumbwheel is correctly rotated to engage the auxiliary function.
  
• The joystick controllers are centered when not in use to avoid unintended hydraulic flow.
  
• Safety interlocks (such as seat bars or operator presence switches) are engaged properly because some machines disable auxiliary hydraulics when these are not activated to prevent accidents.
  

Common Hydraulic Component Issues

• Coupler Problems: Inspect hydraulic quick couplers for dirt, debris, or damage preventing solid connection.
  
• Seal or Cartridge Failures: Rubber seals inside couplers or hydraulic cartridges can degrade with age, causing leaks or loss of pressure.
  
• Valve Block Malfunctions: The auxiliary hydraulic valve block might suffer internal faults, requiring diagnostic equipment or professional service.
  
• Hose Integrity: Check hoses for kinks, leaks, or disconnections that break flow continuity.
  

Electrical System Checks
Since the auxiliary hydraulic system relies on electrical signal transmission to activate valves, verify:

• Integrity of electrical connectors and plugs.
  
• Proper voltage supply to auxiliary hydraulic solenoids.
  
• Continuity of wiring harnesses, avoiding damage or corrosion.
  
• Functionality of switches or thumbwheel sensors.
  

Serial Number and Model Variability
The 236B skid steer exists as several sub-models, including a 236B2 variant, with serial numbers indicating production range and configuration variations. These may influence auxiliary hydraulic circuit design, requiring:

• Reference to the machine’s serial number to obtain accurate diagnostic and wiring diagrams.
  
• Consultation with Caterpillar dealers or manuals specific to the serial range (in this case serial numbers around 6700-7000).
  

Advanced Troubleshooting Tips

• Use diagnostic tools to read fault codes or run hydraulic system tests.
  
• Temporarily bypass or swap hydraulic valves to isolate the fault.
  
• Test auxiliary flow with alternate attachments or lines to rule out attachment-side problems.
  
• Service or replace malfunctioning cartridges or seals identified during inspection.
  

Terminology Explained

• Auxiliary Hydraulics: Additional hydraulic circuit for powering attachments beyond primary machine functions.
  
• Thumbwheel Control: Rotary control on joystick that modulates hydraulic flow for auxiliary systems.
  
• Hydraulic Cartridge: Valve component controlling fluid flow through precise seals and channels.
  
• Quick Coupler: Hydraulic fitting allowing fast attachment connection and release.
  
• Operator Presence System: Safety mechanism detecting seat occupancy to allow hazardous system operation.
  
• Serial Number: Unique identifier used for tracking manufacturing details and matching parts.
  

Real-World Example
A new Cat 236B owner attempted to use a brush cutter attachment but struggled with no auxiliary hydraulic flow. They checked fuses and verified joystick controls but found no resolution. After confirming the serial number and model, they consulted a dealer who suggested inspecting the auxiliary valve block seals and connections. Replacing worn seals restored hydraulic pressure and enabled smooth attachment operation, saving significant downtime.
Summary
Auxiliary hydraulic issues on the Cat 236B skid steer can stem from control misactivation, mechanical wear in valves and seals, electrical faults, or attachment connection problems. A systematic approach to checking control settings, electrical fuses, system cleanliness, and specific hydraulic components is vital. Considering model and serial number specifics enhances troubleshooting precision. With informed diagnostics and maintenance, auxiliary hydraulics functionality can be reliably restored to maximize the utility of the Cat 236B skid steer in varied attachment work.