As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATTEMPTED START OF APU. NO START. INSPECTION OF APU STARTER NOTED HOLE BURNED THROUGH STARTER CASE. REMOVED STARTER AND PERFORMED INSPECTION ON WIRING, TRU, AND APU START CONTACTOR. NO OTHER DAMAGE OR ARCING NOTED. SUSPECT INTERNAL SHORT AND ARCING INSIDE STARTER. INSTALLED REPLACEMENT STARTER IAW AMM 49-41-01, OPS AND LEAK CHECK GOOD.