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Select color for CAS message that you wish to troubleshoot

(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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For AOG assistance contact:

CRC Montreal (YUL)
Quick Links

10/31/24

Message Overview:

Message Name:

AUX BUS LOAD SHED ON GND

Identifier: 246OBS002
Effectivity: 20001 - 20500
System: Cabin Power Distribution
System Description: 24-61-00 - DC Power Center (DCPC)
Schematic Diagram: 24-62-00-101 - Secondary Power Center (SPC) System
Wiring Diagram: 24-61-01-1_001 - DC Power Center (DCPC) Left
24-61-03-1_001 - DC Power Center (DCPC) Right
24-64-01-1_001 - Auxiliary DC Power Center (Aux DCPC)

Message Description:

Aux Bus not powered and no CAS messages on ground.

Possible Causes:

  • Proximity Sensor Electronics Unit (PSEU) (A9)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Notice To Operators (NTO): None

Flight Operation Notifications Manual (FONM): None

NOTE: 

  • The PSEU provides the WOW status that drives the automated load shedding of the AUX Bus.

Quick Links:

Standard Aircraft Configuration for Maintenance AMM 12-00-00-867-803
Electrical/Electronic Safety Precautions AMM 24-00-00-910-801
Electrostatic-Discharge Safety Precautions AMM 24-00-00-910-802
Removal of the Auxiliary Power Contactor AMM 24-61-13-000-801
Installation of the Auxiliary Power Contactor AMM 24-61-13-400-801
Operational Test of the Auxiliary Power Contactor AMM 24-61-13-710-801
Operational Test of the Auxiliary Power Contactor (For Return to Service) AMM 24-61-13-710-802
Operational Test of the Proximity Sensors AMM 32-61-00-710-801
Removal of the Proximity-Sensor Electronic Unit (PSEU) AMM 32-61-09-000-801
Installation of the Proximity-Sensor Electronic Unit (PSEU) AMM 32-61-09-400-801
Functional Test of the Proximity-Sensor Electronic Unit (PSEU) AMM 32-61-09-720-801
Functional Test of the Proximity-System Electronic-Unit Circuitry AMM 32-61-09-720-802

Troubleshooting Recommendations:

  1. Ensure the Aircraft is on ground, weight on wheels condition.
  2. Cycle power to the PSEU.
  3. Is the AUX Bus powered?

    1. If YES, do close out.
    2. If NO, continue with the next step.

  4. Check the MDC to confirm if any faults associated with the Aux Bus or components that are in the circuit path to power the AUX Bus are active.
  5. Troubleshoot active faults before next troubleshooting steps.
  6. Is the AUX Bus powered?

    1. f YES, do close out.
    2. If NO, continue with the next step.

  7. Replace PSEU (A9).
  8. Do close out.

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