What was found
FLIGHT 5831, BTR TO IAH. THE CREW REPORTED A MODERATE ELECTRICAL BURNING SMELL IN THE COCKPIT ON DESCENT FOR ABOUT 30 SECONDS. WHEN THE RECIRCULATION FANS WERE TURNED OFF THE SMELL DISSIPATED. MAINTENANCE RAN THE ENGINES WITH THE CREW ALONG WITH THE PACKS AND OTHER SYSTEMS AND COULD NOT DUPLICATE THE FAULT. THE ODOR RETURNED ON 9/5/2009 AND WAS REPORTED IN CONJUNCTION WITH A GRINDING NOISE COMING FROM THE NR 1 PACK. THE NR 1 PACK WAS THEN DEFERRED. THE PACK FAULT WAS CORRECTED ON 9/6/2009 IN SDF WHEN THE ACM WAS REPLACED DUE TO INTERNAL RUBBING. AFTER REPLACING THE ACM THERE WERE NO FURTHER FAULTS.