APU Fire warning light comes ON when air condition is operating

[Kaydee]

whenever i am running the APU, the fire warning light on both master warning light and the APU T-handle light come up and remain steady once i put ON the air condition. however, if the air condition is not running, the operation of the APU  remains normal. i have tried to check for bleed leaks from he APU to the manifold and no leak was found. pls i need urgent help on what next to look up to pls

[munirabbasi]

13 hours ago, Kaydee said:

whenever i am running the APU, the fire warning light on both master warning light and the APU T-handle light come up and remain steady once i put ON the air condition. however, if the air condition is not running, the operation of the APU  remains normal. i have tried to check for bleed leaks from he APU to the manifold and no leak was found. pls i need urgent help on what next to look up to pls

There no APU Fire alarm system is connected to air-conditioning system .Problem  is APU pneumatic ducting. It might be exhaust duct partial  became  rapture.

Best Regards

Munir Abbasi

Home of Hercules Pakistan

[Kaydee]

9 hours ago, munirabbasi said:

There no APU Fire alarm system is connected to air-conditioning system .Problem  is APU pneumatic ducting. It might be exhaust duct partial  became  rapture.

Best Regards

Munir Abbasi

Home of Hercules Pakistan

Thanks, I will check for that and revert. Grateful

[Kaydee]

Thank u for your invaluable contribution. The fault was traced to a broken clamp on exhaust duct of the APU which allows the exhaust gas fall directly on the sensor loop around it. A new exhaust duct was installed, system tested and found OK.

On 12/27/2020 at 4:12 AM, munirabbasi said:

There no APU Fire alarm system is connected to air-conditioning system .Problem  is APU pneumatic ducting. It might be exhaust duct partial  became  rapture.

Best Regards

Munir Abbasi

Home of Hercules Pakistan

Thanks, I will check for that and revert. Grateful

[NATOPS1]

Check the fire loop element for stand off clearances from all ducts and foil covers. Make sure all the "clamps" are fully insulated from the fire loop as the element can "slip" through the split in the insulation sleeve.

Good luck...

 

APU fire light illuminate with both cargo and flight station AC systems?

Have you "motored" an engine with the condition lever in ground stop so it will not start?