What was found
THE APU FIRE INDICATION LIGHT AND BELL ACTIVATED APPROXIMATELY TWO MINUTES AFTER STARTING APU WHILE DESCENDING INTO DFW. THE APU FIRE BOTTLE WAS DISCHARGED AND THE LIGHT AND BELL WENT OUT. THE AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND WIRES BURNT AT APU THERMOSTAT AND EVIDENCE OF A FUEL STREAM. THE APU WAS RUN AND MAINTENANCE FOUND TORCHING BEING CAUSED BY A FAULTY COMBUSTION CAN. THE APU COMBUSTION CAN WAS REMOVED AND REPLACED. THE APU WIRE HARNESS WAS ALSO REMOVED AND REPLACED. APU LEAK AND OPERATIONAL CHECKS WERE GOOD. IN ADDITION, THE APU FIRE BOTTLE WAS REMOVED AND REPLACED.