As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:N/A DURING CRUISE AT FL270, ALL FIRE WARNING/DET LIGHTS ILLUMINATED MOMENTARILY AND FIRE BELL ALSO RANG MOMENTARILY. THE FIELD OFF AND GEN OPEN LIGHT ON NUMBER 1 GEN WERE ILLUMINATED. REFER TO ITEM 2 AND T/S FOUND THAT FIRE WARNING/DET LIGHT WERE CAUSED BY SWITCHING ELECTRIC POWER TRANSFER. FIRE WARNING OPERATIONAL TEST OK PER AMM 26-11-00 P501, AMM 26-15-00 P501 AND AMM 26-17-00 P501.