As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:N/A REPEAT ITEM (2) - DURING FLIGHT AMBER MX LIGHT ILLUMINATED. TECH RECOMENDS: REVIEW MX HISTORY. DURING SMOKE DETECTOR TEST MX INDICATES ON TWO OCCASIONS THAT SDU FB7739 IS FAULTED. REPLACED BATTERIES, NO HELP. REMOVE AND REPLACE SAID SDU. REPLACED LWR SMOKE DETECTOR FB 7739 PER MM 26-18-00. OPS CHECK GOOD.