The fault code F109 in a PowerFlex 525 drive indicates a mismatch between the control module and the power module. This means there's an incompatibility between the two core components of your drive.

Here's what you can do to troubleshoot the F109 fault:

1. Verify Compatibility: Double-check if the control module and power module are truly mismatched. They should be designed to work together as a specific PowerFlex 525 model. Refer to the drive's manual or markings on the modules themselves to confirm compatibility.
2. Reset Option: In some cases, the F109 fault might be a temporary glitch. You can try resetting the drive using parameter P053 [Reset To Defaults]. However, there are different reset options within P053, so be cautious:
3. Option 1 (Drive Reset): This is the safest option. It resets all drive parameters to factory defaults, but may not clear the F109 fault if there's a genuine mismatch.
4. Option 3 (Power Reset): This option performs a more forceful reset, potentially clearing the fault if it's a glitch. However, it might erase critical drive settings you've programmed.