As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE, APU FIRE LIGHT B LOOP ILLUMINATED WITH BELL. THEN SELECTED LOOP A. AIRCRAFT CONTINUED ON TO ANC AND LANDED WITHOUT INCIDENT. ANC MAINTENANCE PUT APU FIRE LOOP B ON MEL. 18JUL05 SIN MAINTENANCE R&R UPPER FIRE DETECTOR ELEMENTS LOOP A & B. OPERATIONAL CHECKS OK.