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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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Quick Links

05/06/21

Message Overview:

Message Name:

FUSE BLOWN

Message Code:

B3-006319

Associated CAS:

ELECTRICAL FAULT
(Caution)

ELECTRICAL FAULT
(Advisory)

Reporting LRU: APU START FUSE
System Description: 24-31-00
24-64-00
Schematic Diagram: 24-31-10
24-61-00
Wiring Diagram: 24-31-09
24-31-17

Message Description:

The APU Start Fuse has blown.

Possible Causes:

  • APU Start Fuse (APSTF) (F4)
  • Auxiliary Power Center Primary-Logic (ALOG) (PCB11)
  • Auxiliary Power Center (Aux DCPC) (A196)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

Forum Articles/Infoservice/Newsletter: None

Tips:
This fault will most likely not appear alone in the MDC. This fuse will blow when the starting current is reaching more than 500 Amp for few seconds (slow blow fuse).

Verify for other APU Starter related fault(s) in ATA 24 and/or ATA 49 and complete the associated SFP T/S in conjuncture with this one to find the cause of the Fuse blowing.

After a fuse replacement, it is highly recommended to do a complete inspection/verification of the APU starting system before re-trying another APU start and before re-applying the electrical power on the aircraft.

Quick Links:

Removal of the Main Generator AMM 24-31-05-000-801
Installation of the Main Generator AMM 24-31-05-400-801
Removal of the APU Generator AMM 24-31-09-000-801
Installation of the APU Generator AMM 24-31-09-400-801
Removal of the Generator Power Module (GPM) AMM 24-31-21-000-801
Installation of the Generator Power Module (GPM) AMM 24-31-21-400-801
Removal of the Auxiliary Generator Power-Module (AUX GPM) AMM 24-31-25-000-801
Installation of the Auxiliary Generator Power-Module (AUX GPM) AMM 24-31-25-400-801
Removal of the Auxiliary DC Power Center (Aux DCPC) AMM 24-64-01-000-801
Installation of the Auxiliary DC Power Center (Aux DCPC) AMM 24-64-01-400-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02
Electrical Connectors - Maintenance Practice - ALL SPM 20-20-00-02

Troubleshooting Recommendations:

  1. Disconnect both batteries and the External DC power.
  2. Remove, inspect and measure the APU Start Fuse F4 located in the Aux DCPC. Is the fuse good?

    1. If YES, go to step 4.
    2. If NO, continue with next step.

  3. Replace the APU Start Fuse F4 and do a complete inspection/verification of the APU starting system before re-trying another APU start and before re-applying the electrical power on the aircraft.
  4. Replace the Auxiliary Power Center Primary-Logic (PCB11). Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, replace the defective Primary-Logic.

  5. Replace the AUX DCPC (A196).
  6. Do close out.

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