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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

06/28/19

Message Overview:

Fault Message:

GCU4 [H/W OVERVOLTAGE SENSE FAULT]

Fault Code:

2424175LPS

Associated CAS:

GEN 4 FAIL
(Advisory)

Reporting LRU: Generator Control Unit (GCU) 4
System Description: 24-21-00
Schematic Diagram: 24-21-00 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wiring Diagram: 24-21-04 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Fault Description:

Generator Control Unit (GCU) 4 has detected a hardware over-voltage failure on initial power up, consequently preventing the Generator to come on-line.

Possible Causes:

  • Generator Main Exciter Field (MEF)
  • Generator Control Unit (GCU) 4 (A59)
  • Variable Frequency Generators (VFG) 4 (G4)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

A GCU patch cable (GSE REF # 24X-24-02) can be used to swap GCUs 1, 4 and 5 into position 2 or 3 (for troubleshooting only).

The GCU NVMs can only be downloaded at position #2 or #3.

Quick Links:

Electrical/Electronic Safety Precautions AMM 24-00-00-910-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the Variable Frequency Generators (VFG) AMM 24-21-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Variable Frequency Generators (VFG) AMM 24-21-01-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the Generator Control Units (GCU) AMM 24-24-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Generator Control Units (GCU) AMM 24-24-01-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. With connectors GCU 4 (A59P1) and VFG 4 (G4P1) disconnected, perform a check for a short circuit (See Quick Links: WIRING I/F-GCU4/VFG4) as follows:

    From To Result
    G4P1-B Ground

    1. If a short to ground fault is detected, repair or replace defective wiring as required and do close out.
    2. If no short to ground fault is detected, continue with next step.
      NOTE: Megohmmeter may be required to detect short.

  2. Swap the GCU 4 with GCU 3 (or use the patch cable).

    1. If system checks are good, replace GCU 4 and do close out.
    2. If fault remains, continue with next step.

  3. Replace VFG 4.
  4. Do close out.

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