As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT, APU FIRE LIGHT ILLUMINATED WITH THE APU OFF. ON SECOND OCCURRENCE, APU FIRE HANDLE PULLED, BOTTLE DISCHARGED, AND RETURNED TO FIELD. INSPECTED APU OVERHEAT DETECTION SYSTEM AND FOUND A SHORT TO GROUND AT CONNECTOR D4934P ON BOTH PINS A & C. REPLACED CONNECTORS D1876 AND D1878. APU FIRE DETECTION SYSTEM CHECKED GOOD.