As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON PREFLIGHT TRANSIT CHECK APU FIRE WARNING HORN IN MAIN WHEEL WELL SOUNDED CONTINUALLY WITH APU OFF. ENGINE/APU FIRE DETECTOR BOX TESTS NORMAL. NO WHEEL WELL LIGHT FLASHING. TROUBLESHOT SYSTEM, FOUND APU WARNING HORN AT FAULT. REMOVED AND REPLACED WARNING HORN. OPERATIONAL CHECK NORMAL. RETURNED AIRCRAFT TO SERVICE. (K)