How do i know if my cruise control manifold is defective on a 2005 Ford f 150

Hello, what is a "cruise control manifold"? Typically, your cruise control system will not operate at all if any of the related components are not working properly -- such as the brake cut off switch. It would be highly unusual to have the system operational without a method of deactivation. I would inspect all components of the system using a Ford IDS diagnostic tool (or equivalent), which should be used to monitor all components of the cruise control system operation.