As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER SHUT DOWN OF APU HAD FIRE INDICATION OF RED LIGHT IN FIRE SWITCH WITH EGT OF 550 DEGREES. PULLED FIRE SWITCH AND DISCHARGED BOTTLE. FIRE INDICATIONS WENT OUT AFTER THAT. VISUALLY INSPECTED APU AND NO EVIDENCE OF FIRE FOUND. REMOVED AND REPLACED APU FIRE BOTTLE PER MM 26-23-1. FOUND APU OVERHEAT DISCHARGE LINE BROKEN. REPLACED APU OVERHEAT DISCHARGE LINE. SYSTEM OPERATIONS CHECK GOOD.