As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT ON FLIGHT 3009 REPORTED TO MAINTENANCE CONTROL THE MID CABIN DC AUX HEATER WAS EXPELLING SPARKS OUT VENT IN ROW 6, AND SMELLED HOT (ELECTRICAL SMELL). MAINTENANCE INSPECTED ROW 6 HEATER, NO ELECTRICAL SMELL NOTICED. REMOVED HEATER SHROUD, CLEANED SMALL PAPERS AND DEBRIS FROM HEATER. RAN HEATER FOR 1015 MINUTES. NO SMELL AND NORMAL OPERATION.