As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FAY, CREW REPORTED VIBRATION AND BURNT / ELECTRICAL SMELL ON APU START. LEFT PACK WENT TO 36° C. MAINTENANCE INSPECTED, REMOVED AND REPLACED LEFT ACM (AIR CYCLE MACHINE) AND PERFORMED CHECKS USING AIRCRAFT MAINTENANCE MANUALS. AIRCRAFT RELEASED FOR SERVICE.