As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, APU FIRE WARNING BELL AND LIGHT ACTIVATED AT FL 110. DISCHARGE APU FIRE BOTTLE AND LIGHT WENT OUT. 2 MINUTES LATER, LIGHT AND BELL CAME BACK ON AGAIN. FOUND BROKEN WIRE AT APU WIRE BUNDLE SI NR 2491548. REMOVED AND REPLACED WIRE AND OPS CK GOOD PER MM.