As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACFT EXPERIENCED AN INFLIGHT FIRE WARNING HORN BUT NO WARNING LIGHT. FIRE BOTTLE WAS DISCHARGED INTO NR 1 ENGINE ON SHUTDOWN AS THE ENGINE PASSED 50 PERCENT AS DESIGNED. TROUBLESHOOTING REVEALED THE FWD FIRE DETECTOR TO HAVE A HIGH RESISTANCE SHORT. UNIT INDICATES A 850K OHM SHORT RISING TO 900K OHM THE LONGER THE DVOM IS HELD ON THE TERMINALS. SWITCHING THE LEADS THE UNIT INDICATES AN OPEN.