As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU starter/generator inoperative. Removed and replaced unit.In addition to normal wear as compared to other units at overhaul, the following items were noted on teardown report:Commutator pitted and heavily groovedDrive and bearing retainer damagedSpeed sensor assembly and speed sensor disc damagedArmature out of balanceBearings dry and heavily contaminatedCatastrophic DE bearing failureDamage due to bearing failure