Prerequisites:
Determine the name of the custom action you want to debug
Ensure you have the source code and debug symbols for your custom action
Steps
Set the MsiBreak environment variable (user or system) to the name of the custom action. For example:
Setx MsiBreak MyCustomActionName
Run your installer
At the point where your custom action is about to run, you should get . . . → Read More: HOW TO: Debug a Windows Installer custom action