As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 2553 - CREW REPORTED A BURNING SMELL IN THE COCKPIT AND CABIN WHEN THE AIR CONDITIONING PACKS WERE SELECTED TO MANUAL. MAINTENANCE CLEANED THE LEFT AIR CONDITIONING PACK SPRAY NOZZLE, OPERATIONALLY CHECKED THE SYSTEM AND CLEARED THE DISCREPANCY.