Cause : CU: Control module overtemperature - When encountering a "CU: Control module overtemperature" error on a Siemens G120 drive, it indicates that the control module within the drive has reached a temperature above the specified threshold. This can happen due to various reasons, including inadequate cooling, high ambient temperatures, or internal faults. Here's how you can troubleshoot and address this issue:

1. Check Ambient Temperature: Ensure that the operating environment of the drive is within the specified temperature range as per the drive's documentation. High ambient temperatures can contribute to overheating issues. If the ambient temperature is too high, consider improving ventilation or adding additional cooling devices to the enclosure.

2. Inspect Cooling System: Check if the cooling system (fans, heatsinks, etc.) of the drive is functioning properly. Make sure that the fans are operational and not obstructed by dust or debris. Clean the cooling system if necessary and ensure proper airflow around the drive.

3. Verify Load Conditions: High load conditions can lead to increased heat generation within the drive. Check the load conditions on the drive and ensure that it's operating within its rated capacity. If necessary, reduce the load or distribute it among multiple drives.

4. Check Drive Installation: Ensure that the drive is installed correctly according to the manufacturer's guidelines. Improper installation can restrict airflow or cause heat buildup. Verify that the drive is mounted securely and positioned in a way that allows for adequate ventilation.

5. Inspect Drive Components: Inspect the drive components for any signs of damage or wear that could affect its cooling efficiency. Replace any damaged components and ensure that all connections are secure.

6. Reduce Ambient Temperature: If possible, reduce the ambient temperature around the drive by improving ventilation, relocating the drive to a cooler area, or installing additional cooling equipment such as air conditioners or heat exchangers.

7. Monitor Drive Temperature: Use diagnostic tools provided by Siemens to monitor the temperature of the drive in real-time. This can help you identify patterns or trends that may indicate underlying issues contributing to overheating.