As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER DEFERRING THE APU DOOR OPEN, DURING THE APU START, BLUE SMOKE WAS REPORTED IN THE COCKPIT ALONG WITH AN APU FIRE 'W' MESSAGE. ON INSPECTION, BURNED & MELTED WIRING WAS FOUND AROUND THE APU, BUT WAS CONTAINED TO JUST THE APU AREA. MX R & R THE APU AND APU FIRE BOTTLE. NO OTHER DEFECTS NOTED.