As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU WILL NOT START. HANGS BETWEEN 25 AND 35 PERCENT RPM AND SHUTS DOWN WITH FAULT LIGHT ON. CREW COMMENTS: HANGS AT 27. BATTERY SHOWS 28V, CHIP DETECTOR CHECKED, NO METAL ON CD, APU STARTER MOTOR REPLACED IAW AMM. 2 SUCCESSFUL STARTS PERFORMED WITHOUT PROBLEM.