As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE-N/A, AIR TURNBACK DUE TO NR 3 FIRE BELL INADVERTENTLY RINGING. NR 3 FIRE DETECT CIRCUIT WOULD NOT TEST IN FIRE TEST POSITION OR SHORT CIRCUIT TEST. REMOVED AND REPLACED PYLON LOOP PER MM 26-10-00, DUE TO HISTORY AND AGE. FOUND BLEED AIR LINE ADJ TO FIRE LOOP LOOSE AND RESULTING IN HOT AIR OVER LOOP. TIGHTENED SAME. REMOVED AND REPLACED 5 LOOP CONNECTORS PER EO DC8-2610-4683-D DUE TO AGE. RAN NR 3 FIRE WARNING TEST, NO DEFECTS.