What was found
DURING APU START AND WHEN APU MASTER SWITCH PUSHED, APU FIRE BOTTLE UNCOMMAND DISCHARGED HAPPENED. VISUAL CHECK PERFORMED, FOUND APU FIRE BOTTLE EMPTY, REFER TO ATL SEQ. #11268. PERFORMED FULL WIRING CHECK IAW WDM 26-21-00 REV. 31 DATED JUL 2011, ALL FOUND SATISFACTORY. APU PLACARDED INOPERATIVE UNDER MEL 26-12-01 CATEGORY C, REFER TO ATL SEQ. #11271. FULL WIRING CHECK ITW WDM 26-21-00 REV. 31 DATED JUL 2011, ALL FOUND SATISFACTORY (ATL SEQ.#11271). REPLACED APU FIRE BOTTLE DISCHARGE SWITCH (PRECAUTIONARY) IA W AMM 49-00-00 REV. 34 DATED 04 MAR 2022 (ATL SEQ. #11293). REPLACED APU FIRE BOTTLE IA W AMM 26-02-00 REV. 34 DATED 04 MAR 2022 (ATL SEQ. #11292. APU OPERATIONAL CHECK FOUND SATISFACTORY.