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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

01/25/21

Message Overview:

R ESS BUS FAIL
(Caution)

DDG Reference: None
Pilot Action (QRH): ELEC 04-5
System Description: 24-00-00
Schematic Diagram: 24-31-00
Wiring Diagram: 24-00-00

Message Description:

The amber 'R ESS BUS FAIL' caution CAS message indicates the Right Essential Power Bus has no power, although it is available. This CAS will be posted when one or more associated relay(s) is (are) not operating properly.

Each DC Power Control Center has a 400 Amp Auxiliary power contactor (Relay) that is automatically controlled by the power center.

Possible Causes:

  • Electrical System Component(s)

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

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
Removal of the DC Power-Center Fuses AMM 24-61-79-000-801
Installation of the DC Power-Center Fuses AMM 24-61-79-400-801
Removal of the DC Power-Center Relays AMM 24-61-81-000-801
Installation of the DC Power-Center Relays AMM 24-61-81-400-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Check on the EICAS page for other ATA 24 related faults and proceed with respective troubleshooting.
  2. 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 fault. Going into advanced diagnostics will provide an equation id for the fault identified.
    3. Select the MDC fault or equation from the drop down below to provide additional information to assist in troubleshooting.

45_advance_diagnostics

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