If the carafe is not centered on the heat plate, then the coffee will not flow into the carafe and will fill the filter and overflow as it cannot hold 8-12 cups. There is a plastic bump on the top of the carafe that pushes against a valve in the filter section. If the carafe is fully centered on the heat plate, then the valve will open and allow coffee to flow into the carafe. If not fully centered, then bad news. Hope this helps.