Causes of a refrigerator to stop cooling and ice forming on back of frost free freezer?

seriously nothing being said about automatic defrost and defrost timer ...could be that its not going through its defrost cycle meaning its stuck on cooling cycle and creating your frost in freezer means bad defrost timer,not going into defrost mode ..old units have manual timers new refrigeraters have computer boards.try unplugging refrigerater for 24hrs open door and let defrost, then plug in, if you get refrigerator to cool that next day ...more then likely its the defroster timer