Troubleshooting Terex Demag AC 55-2012: Resolving the 'Lock Symbol' and Starting Issues

[MikePhua]

The Terex Demag AC 55-2012 is a powerful and versatile all-terrain crane used in construction, heavy lifting, and industrial applications. While this crane is known for its reliability and high performance, like any complex machinery, it can experience issues from time to time. One such issue that some operators have reported is the machine failing to start, accompanied by a "lock symbol" appearing on the display.
In this article, we will discuss the potential causes of this problem, how to troubleshoot it effectively, and the steps you can take to resolve the issue and get your Terex Demag AC 55-2012 back to work.
Understanding the 'Lock Symbol' on the Terex Demag AC 55-2012
The "lock symbol" on the Terex Demag AC 55-2012 crane typically indicates that the crane's safety system is engaged, preventing it from starting. This safety mechanism is in place to prevent accidents and ensure the crane is operated within safe parameters. However, when the lock symbol appears and the crane fails to start, it can be frustrating and hinder progress on the job site.
The lock symbol often suggests that the crane's control system is detecting a fault or that one of the necessary safety protocols has been triggered. This could be related to the crane’s electrical system, hydraulics, or even an issue with the crane’s safety sensors.
Common Causes of the 'Lock Symbol' and Starting Issues
Several factors could be causing the "lock symbol" to appear and prevent the Terex Demag AC 55-2012 from starting. Understanding the most common causes of this issue can help you troubleshoot the crane more efficiently. Here are some potential causes:

1. Battery or Electrical System Issues
   If the crane’s electrical system is malfunctioning, it can cause the lock symbol to appear. A dead or weak battery, poor connections, or faulty wiring can all trigger a safety lockout. The crane's system may detect an electrical fault and prevent the engine from starting to avoid further damage.
   Solution: Inspect the battery for charge levels and ensure all electrical connections are secure. If the battery is low, charge or replace it. Also, check for any loose or corroded wiring connections that could be disrupting the electrical flow. If necessary, use a multimeter to check the voltage levels of the crane's electrical system.
   
2. Hydraulic System Lockout
   The Terex Demag AC 55-2012, like many cranes, has a hydraulic system lockout feature that is activated if the hydraulic system is not in the proper operating condition. This could be due to low fluid levels, air in the system, or a malfunctioning hydraulic pump.
   Solution: Check the hydraulic fluid levels and ensure that they are within the recommended range. If the fluid is low, top it up with the appropriate fluid. Also, inspect the hydraulic hoses and connections for any signs of leaks or damage. If the hydraulic pump is malfunctioning, it may need to be repaired or replaced.
   
3. Safety Interlock System Activation
   Cranes like the Terex Demag AC 55-2012 are equipped with safety interlock systems that prevent the crane from starting unless all safety conditions are met. If the system detects an issue, such as a malfunctioning sensor or an unsecure load, it will engage the lock symbol to prevent the crane from operating.
   Solution: Ensure that all safety interlocks are correctly engaged. This includes checking that the load is secure and that all safety sensors are functioning properly. If there are any issues with the sensors or interlocks, these will need to be addressed before the crane can be started.
   
4. Faulty Control Panel or Software Glitch
   The control system of the Terex Demag AC 55-2012 is highly sophisticated, and a software glitch or malfunctioning control panel can trigger the lock symbol. If the control panel is not properly communicating with the crane’s systems, it may interpret this as a fault and engage the safety lockout.
   Solution: Reset the crane’s control system by powering it off and then restarting it. If the lock symbol persists, it may be necessary to perform a diagnostic check using the crane’s onboard diagnostic system or consult with a technician to address any software-related issues.
   
5. Overloaded or Incorrect Configuration
   Overloading the crane or setting it up incorrectly for the task at hand can also trigger the lock symbol. The Terex Demag AC 55-2012 has built-in load limiters and other safety features that are designed to prevent the crane from operating under unsafe conditions.
   Solution: Check the crane’s load chart and ensure that the crane is not overloaded. Make sure that the crane is configured correctly for the job at hand, and all outriggers and stabilizers are properly deployed and secure.
   

Step-by-Step Troubleshooting Guide for the Terex Demag AC 55-2012
If your Terex Demag AC 55-2012 is showing the lock symbol and failing to start, follow this step-by-step guide to troubleshoot the issue:

1. Step 1: Check the Battery and Electrical System
   • Verify that the battery is charged and in good condition.
     
   • Inspect all wiring connections and ensure they are clean, tight, and free from corrosion.
     
   • Use a multimeter to test the electrical system and confirm that the voltage levels are within the acceptable range.
     
2. Step 2: Inspect the Hydraulic System
   • Check the hydraulic fluid levels and ensure they are topped up to the recommended levels.
     
   • Inspect hydraulic hoses and connections for any signs of leaks or damage.
     
   • If necessary, bleed the hydraulic system to remove air pockets and restore pressure.
     
3. Step 3: Verify Safety Interlocks and Sensors
   • Ensure that all safety interlocks are properly engaged and that the load is secure.
     
   • Inspect sensors, including the load and outrigger sensors, to ensure they are functioning correctly.
     
   • If any sensors appear to be malfunctioning, have them repaired or replaced.
     
4. Step 4: Reset the Control Panel
   • Power off the crane completely and restart it to see if the lock symbol disappears.
     
   • Perform a diagnostic check using the onboard diagnostic system to identify any software-related issues.
     
5. Step 5: Check for Overload or Configuration Issues
   • Verify that the crane is not overloaded and is configured correctly for the job.
     
   • Consult the crane’s load chart to ensure that the load limits are not exceeded.
     
   • Check that all outriggers and stabilizers are deployed correctly.
     

Preventative Maintenance to Avoid Future Starting Issues
Preventative maintenance is key to ensuring that your Terex Demag AC 55-2012 remains in optimal condition and avoids starting issues like the "lock symbol." Here are some preventative measures you can take:

1. Regularly Inspect the Battery and Electrical System
   • Perform regular battery maintenance to ensure it stays charged and free from corrosion.
     
   • Check wiring connections and electrical components for wear or damage.
     
2. Maintain the Hydraulic System
   • Regularly check hydraulic fluid levels and replace fluid as necessary.
     
   • Inspect hydraulic hoses and fittings for leaks, and clean the hydraulic filters periodically.
     
3. Test Safety Sensors and Interlocks
   • Periodically test the safety interlocks and sensors to ensure they are functioning correctly.
     
   • Make sure that the load chart and load limits are adhered to during operations.
     
4. Software Updates and Control System Maintenance
   • Keep the crane’s control system software up to date to avoid glitches and bugs.
     
   • Regularly reset the system to clear any potential errors and ensure smooth operation.
     

Conclusion: Keeping Your Terex Demag AC 55-2012 in Top Shape
The "lock symbol" issue on the Terex Demag AC 55-2012 can be frustrating, but with the right troubleshooting steps, you can quickly identify the cause and resolve the issue. Whether it’s an electrical problem, hydraulic malfunction, or safety system trigger, understanding the common causes will help you fix the problem efficiently.
By maintaining your crane with regular checks, preventative maintenance, and timely repairs, you can avoid this issue and ensure that your Terex Demag AC 55-2012 continues to perform reliably on the job site. When in doubt, don’t hesitate to consult a qualified technician for further assistance.