As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE TO TOL TO PHX, THE AIRCRAFT HAD THE FIRE WARNING BELL CAME ON WITHOUT ANY WARNING LIGHT INDICATION AS TO WHICH ENGINE OR ANY OTHER INDICATIONS DURING CRUISE. THE AIRCRAFT LANDED WITHOUT ANY FURTHER DIFFICULTIES. REMOVED AND REPLACED THE NR 1 FIRE WARNING POWER SUPPLY UNIT. OPERATIONALLY CHECKS NORMAL TO GROUND. THE AIRCRAFT IS RETURNED TO SERVICE. (M)