Cruise control has a vacuum line in the cab on the brake booster rod, it releases vacuum in cruise module if brake is applied, it is an emergency cut off if brake light switch isn't working.
Called the dump valve, seen in this drawing: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Cruisecontrol_1of2.JPG
Check both ends of that hose and the hose itself
Called the dump valve, seen in this drawing: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Cruisecontrol_1of2.JPG
Check both ends of that hose and the hose itself