As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: DURING THE CLIMB PHASE, THE APU FIRE DISCHARGE LIGHT ILLUMINATED. THERE WAS NO OTHER INDICATIONS PRESENT. APU WAS NOT STARTED ON TAXI IN TO GATE UPON ARRIVAL. MAINTENANCE PERFORMED BITE TEST OF THE APU FIRE AND OVERHEAT DETECTION SYSTEM PER AMM 26-13-00-710-002-A PER TSM 26-136-00-810-802-A WITH NO MESSAGE FOUND. DURING AN OPERATIONAL TEST OF THE APU THE FIRE DISCHARGE LIGHT DID NOT ILLUMINATE.