How to change a field value with a Rules Action? I'm trying to set up a Rules  Action that can change the value of a field. I created an Action Set with a data type of Node. When I go to create a Rules Action, I have access to every default Drupal node field, but no fields.

Is this simply not possible? Do I need some other module to make this work?
You first need to add a condition to check if the field exist on that node, only then it is available to the actions. There is a specific condition to do this.