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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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01/28/21

Message Overview:

APU FAULT
(Advisory)

DDG Reference: 49-11
Pilot Action (QRH): APU 01-5
System Description: 49-70-00
Schematic Diagram: 49-61-00
Wiring Diagram: 49-61-01

Message Description:

The cyan 'APU FAULT' advisory CAS message indicates a fault has been detected in the APU system.

  • Either a bleed valve, fuel solenoid, start prevented, or avionics are not communicating with the electronic control unit.
  • Typically there are three items that typically fail for these faults, EGT probe opening up and displaying EGT in dashes, Fuel shut-off valves sticking closed with no lite-off (no fuel vapor seen from APU exhaust), and failed igniter (no lite-off with fuel vapor in the exhaust).
  • The DCU has posted this fault because of lack of communication with the ESU.

Possible Causes:

  • None

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

None

Troubleshooting Recommendations:

  1. Interrogate the MDC as follows:

    1. On the cursor control panel, ensure the toggle switch is to the right and select Anti-Ice, ECS and Fuel buttons simultaneously. The MDC main menu should now be displayed on Display Unit #3.
    2. Using the joystick, select Current Faults (if the fault is active) or Aircraft History to research stored faults. From Aircraft History you can then select Fault Message History and locate the air condition fault logged.
    3. Check the Current Service Message and Service Message History to look for messages associated with the APU, troubleshoot as required when identified.

45_current_faults

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