Pulling the APU Fire Switch :
- closes the APU Fuel SOV
- closes the APU Bleed Air Valve
- trips the APU GCR and GCB
- closes the APU inlet Door
- arms the discharge squib on the APU Fire Extinguisher
(As Installed) APU Fire Extinguisher automatic discharge :
APU fire detected, Air/Gnd sensor in GND mode, Both engines NOT running and APU fire extinguisher automatic discharge