As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: RECIRCULATION FAN STATUS MESSAGE. ELECTRIC BURNING SMELL IN MAIN CABIN. RECIRCULATION FANS TURNED OFF, SMELL DISSIPATED. MAINTENANCE FOUND AFT UPPER RECIRCULATION FAN OVERHEAT FAULT CODE 21-24500. REPLACED RECIRCULATION FAN PER AMM 21-25-01. ACCOMPLISHED SATISFACTORY OPERATIONAL CHECK.