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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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09/21/20

Message Overview:

Fault Message:

GCU2 [GLC DRIVE OPEN/SHORT/STATUS]

Fault Code:

2422133LPS

Associated CAS:

GEN 2 FAIL
(Advisory)

Reporting LRU: Generator Control Unit (GCU) 2
System Description: 24-21-00
Schematic Diagram: 24-21-00 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wiring Diagram: 24-21-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Fault Description:

The Generator Control Unit (GCU) has detected a malfunction with the Generator Line Contactor (GLC) Coil and or the GLC status reporting.

Possible Causes:

  • Generator Control Unit (GCU) 2 (A57)
  • Generator Line Contactor (GLC)
  • AC Power Center (ACPC) (A54)
  • 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:

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 ]
Removal of the AC Power Center (ACPC) AMM 24-51-00-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the AC Power Center (ACPC) AMM 24-51-00-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the AC Power Center (ACPC) Primary Logic AMM 24-51-09-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the AC Power Center (ACPC) Primary Logic AMM 24-51-09-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the AC Power Center (ACPC) L-Series Contactors AMM 24-51-33-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the AC Power Center (ACPC) L-Series Contactors AMM 24-51-33-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]
AC Power Center Component Maintenance Manual CMM 24-51-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. Swap GCU 2 with GCU 3.

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

  2. Perform wiring checks on the GLC drive circuit for the ground short fault. On the GCU 2, disconnect connector A57P1 and on the ACPC, gain access to the ACPC primary distribution section and disconnect connector P203 of GLC 2 and on connector A57P1, using a multi-meter, check for a ground on A57P1-P.

    1. If a ground short fault is not detected, go to step 5.
    2. If a ground short fault is detected, continue with next step.

  3. On the ACPC, disconnect connector A54P7 and on connector A57P1, using a multi-meter, check for a ground on A57P1-P.

    1. If the ground short fault is still present on A57P1-P, repair or replace the defective wiring between the GCU 2 and the ACPC and do close out.
    2. If the ground short fault is no longer present on A57P1-P, continue with next step.

  4. Check for ground on GLC 2 connector P203-1.

    1. If a ground is present, repair the defective wiring between connector P203-1 and receptacle A54J7-K and do close out.
    2. If unable to repair the wire, replace ACPC and do close out.
    3. If a ground is not present, continue with next step.

  5. Perform wiring checks on the GLC drive circuit for the open circuit fault. On the GCU 2, disconnect connector A57P1 and on the ACPC, disconnect connector P203 of GLC 2. Check for an open circuit between A57P1 and GLC 2 connector as follows:

    From To Expected Result Result
    A57P1-P P203-1 open

    1. If an open circuit fault is not detected, go to step 8.
    2. If an open circuit fault is detected, continue with next step.

  6. On the ACPC, disconnect connector A54P7. Check for an open circuit between A57P1 and A54P7 as follows:

    From To Expected Result Result
    A57P1-P A54P7-K open

    1. If the open circuit fault is still present, repair or replace the defective wiring between the GCU 2 and the ACPC and do close out.
    2. If the open circuit fault is no longer present, continue with next step.

  7. Check for an open circuit between A54J7 and GLC 2 connector as follows:

    From To Expected Result Result
    A54J7-K P203-1 open

    1. If the open circuit fault is present, repair the defective wiring between connector P203-1 and receptacle A54J7-K and do close out.
    2. If unable to repair the wire, replace ACPC and do close out.
    3. If the open circuit fault is not present, continue with next step.

  8. Disconnect GLC 2 connector P203. Check for a ground on connector P203-22.

    1. If the ground is missing, repair defective wiring between P203-22, TB201, TB601 and ground stud E001 and do close out.
    2. If unable to repair the wire, replace ACPC and do close out.
    3. If the ground is present, continue with next step.

  9. Replace GLC 2.

    1. If the system checks are good, do close out.
    2. If the fault remains, continue with next step.

  10. Perform wiring checks on the GLC status circuit for the ground short fault. On the GCU 2, disconnect connector A57P2. On ACPC, gain access to the ACPC primary distribution section and disconnect connector P203 of GLC 2.
  11. On connector A57P2, using a multi-meter, check for a ground on A57P2-19.

    1. If a ground short fault is detected, go to step 17.
    2. If a ground short fault is detected, continue with next step.

  12. On ACPC, disconnect connector A54P7. On connector A57P2, using multi-meter check for a ground on A57P2-19.

    1. If the ground short fault is no longer present on A57P2-19, continue with next step.
    2. If the ground short fault is still present, repair or replace the defective wiring between GCU 2 and the ACPC and do close out.

  13. On GLC2 connector P203, check for a ground on P203-8.

    1. If a ground is present, repair the defective wiring between connector P203-8 and receptacle A54J7-c and do close out.
    2. If unable to repair the wire, replace ACPC and do close out.
    3. If a ground is not present, continue with next step.

  14. Perform wiring checks on the GLC status circuit for the open circuit fault. On the GCU 2, disconnect connector A57P2. On ACPC, disconnect connector P203 of GLC 2. Check for open circuit as follows:

    From To Expected Result Result
    A57P2-17 P203-8 open

    1. If no open circuit fault is detected, go to step 17.
    2. If an open circuit fault is detected, continue with next step.

  15. On ACPC, disconnect connector A54P7. Check for an open circuit as follows:

    From To Expected Result Result
    A57P2-19 A54P7-c open

    1. If the open circuit fault is still present, repair or replace the defective wiring between GCU 2 and the ACPC and do close out.
    2. If the open circuit fault is no longer present, continue with next step.

  16. Check for an open circuit as follows:

    From To Expected Result Result
    A54J7-c P203-8 open

    1. If an open circuit fault is still present, repair the defective wiring between connector P203-8 and receptacle A54J7-c and do close out.
    2. If unable to repair the wire, replace the ACPC and do close out.
    3. If an open circuit fault is not present, continue with next step.

  17. Disconnect GLC 2 connector P203. Check for a ground on connector P203-9.

    1. If the ground is missing, repair defective wiring between P203-9, TB201, TB601 and ground stud E001 and do close out.
    2. If unable to repair the wiring, replace the ACPC and do close out.
    3. If the ground is present, continue with next step.

  18. Replace GLC 2.
  19. Do close out.
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