I recently experienced a similar problem with my F-150. You should read my posting dated 02-04-2004 for my solution named DRH- F-150 Cruise Defect. If the cruise disabling switch is not the problem you can check for power at the cruise servo by unplugging the terminal block at the servo and testing pin no. 7 for voltage with the ignition switched on. If you do have power and the disabling switch checks O.K. then the buttons on the steering wheel may need cleaning(see previous postings) or worst of all, a bad servo. Good luck.