As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMELL OF BURNING RUBBER AROUND 18K. RAN ENGINES W APU ON AIR GROUNDS OPEN HYDRAULICS AND PACKS RUNNING INSPECTED MAIN BATT 1,2 & BACKUP RELAY BOX. INSPECTED RIGHT & LEFT HAND RELAY SUPPORT AND RIGHT & LEFT POWER CONTROL DIST BOXES INSPECTED BOTH PACK 1 & 2 NO SMELL OF BURNING RUBBER. A/C OK FOR SERVICE