As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ELECTRICAL BURNING SMELL WHEN APU BLEED IS ON AROUND MIDDLE CABIN AREA. INSPECTED OVERHEAD AND SIDEWALL LIGHTS NO BURNS OR ANY DEFECTS NOTED FROM MIDDLE TO AFT CABIN (SHORT SIGNED BY 9452). GROUND RAN AIRCRAFT OPERATED ENGINES AND AUXILIARY POWER UNIT BLEEDS, CHECKED AIR CYCLE MACHINE OIL LEVEL ALL CHECKED GOOD. SMELL DISSIPATED, OK FOR SERVICE.