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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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02/25/21

Message Overview:

Message Name:

HYD GEN ISOL VALVE FAIL

Message Code:

B3-374379

Associated CAS:

ELEC HYD GEN FAIL
(Caution)

Reporting LRU: HYD GEN
System Description: 24-33-00
Schematic Diagram: 24-33-00
Wiring Diagram: 24-33-01
24-33-03

Message Description:

The HYD GEN Isolation Valve is failed partially or fully open.

Possible Causes:

  • Hydraulic-Motor Driven Generator (HMDG) (G4)
  • Hydraulic-Motor Driven Generator Control Unit (HMDG GCU) (A206)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

  • SB100-24-04 - MODIFICATION - EMERGENCY DC-POWER SYSTEM - Installation of the Hydraulic Motor Driven Generator (HMDG) Option (C24-300)

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Operational Test of the HMDG System AMM 24-33-00-710-801
Removal of the Hydraulic-Motor Driven Generator (HMDG) AMM 24-33-01-000-801
Installation of the Hydraulic-Motor Driven Generator (HMDG) AMM 24-33-01-400-801
Removal of the Generator Control Unit (GCU)-Emergency AMM 24-33-09-000-801
Installation of the Generator Control Unit (GCU)-Emergency AMM 24-33-09-400-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Do wiring check as per the following table:

    From To Results
    HMDG GCU conn A206P2 - pin A HMDG conn G4P4 - pin 1
    HMDG GCU conn A206P2 - pin B HMDG conn G4P4 - pin 2
    HMDG GCU conn A206P2 - pin M HMDG conn G4P3 - pin C
    HMDG GCU conn A206P2 - pin P Aircraft Ground

    1. If the check is not satisfactory, repair/replace defective wiring.
    2. If the check is satisfactory, continue with next step.

  2. Replace HMDG (G4). Is the fault still present?

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

  3. Replace HMDG GCU (A206).
  4. Do close out.

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