As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB WITH NR 4 ENGINE FIRE LOOP -A- ON MEL, THE FAULT DETECTION ANNUNCIATOR ILLUMINATED FOR THE NR 4 ENGINE B-FIRE DETECTOR. AIRCRAFT RETURNED TO ANC AND LANDED WITHOUT INCIDENT. REPLACED TERMINALS FOR (A) AND (B) FIRE LOOPS AND REPLACED THE RIGHT SIDE SEGMENT OF THE UPPER CORE FIRE LOOP. OPERATIONAL CHECK GOOD.