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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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06/10/21

Message Overview:

Message Name:

APU GEN DELTA CURRENT FAULT

Message Code:

2420118LPS

Associated CAS:

APU GEN FAIL
(Advisory)

Reporting LRU: Auxiliary Power Unit (APU) Generator Control Unit (GCU)
System Description: 24-22-00
Schematic Diagram: 24-22-00 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wiring Diagram: 24-22-01 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Message Description:

Auxiliary Power Unit (APU) Generator Control Unit (GCU) detects between two phases a difference in output current larger than 35 amps ±5 amps.

Possible Causes:

  • Auxiliary Power Unit (APU) Generator Control Unit (GCU) (A109)
  • Auxiliary Power Unit (APU) Generator (A110)
  • AC Power Center (ACPC) (A54)
  • 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

A GCU patch cable (GSE REF # 24X-24-02) can be used to interchange 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.

gcu_patch_cable

Quick Links:

Removal of the APU Generator AMM 24-22-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the APU Generator AMM 24-22-01-400-801 [ 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 ]
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) ZJC-Series Contactor (K1) AMM 24-51-41-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the AC Power Center (ACPC) ZJC-Series Contactor (K1) AMM 24-51-41-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the AC Power Center (ACPC) Line Current Transformers AMM 24-51-49-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the AC Power Center (ACPC) Line Current Transformers AMM 24-51-49-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. Check for CAIMS message related to the ACPC short circuit fault. Clear/troubleshoot the message first if existed.

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

  2. Interchange APU GCU with GCU #2 (physically or using the GCU patch cable).
    NOTE: Use PMAT to monitor the fault on GCU.

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

  3. Disconnect T1, T2, T3 and G at APU GEN.
  4. Perform continuity checks (open circuit = failure) at the terminal block of APU GEN as follow:

    From To Result
    A110P1-T1 A110P1-G
    A110P1-T2 A110P1-G
    A110P1-T3 A110P1-G

    1. If there is no continuity, go to step 26.
    2. If there is continuity, continue with next step.

  5. Perform continuity checks (closed circuit = failure) at the terminal block of APU GEN as follow:

    From To Result
    A110P1-T1 Ground
    A110P1-T2 Ground
    A110P1-T3 Ground

    1. If there is continuity, go to step 26.
    2. If there is no continuity, continue with next step.

  6. Perform wiring checks (open circuit = failure) between APU GEN and ACPC as follow:

    From To Result
    A110P1-T1 A54P4-T13
    A110P1-T2 A54P4-T14
    A110P1-T3 A54P4-T15

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  7. Disconnect connector A110P1 on the APU GEN.
  8. Perform continuity checks (closed circuit = failure) on APU GEN and ground as follow:

    From To Result
    A110P1-F Ground
    A110P1-E Ground
    A110P1-J Ground
    A110P1-D Ground

    1. If there is no continuity, go to step 26.
    2. If there is no continuity, continue with next step.

  9. Disconnect APU GCU connector A109P2.
  10. Perform wiring checks (open circuit = failure) between A110P1 and A109P2 as follow:

    From To Result
    A110P1-F A109P2-41
    A110P1-E A109P2-42
    A110P1-J A109P2-50
    A110P1-D A109P2-40

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  11. Perform wiring checks (closed circuit = failure) between A110P1 and ground as follow:

    From To Result
    A110P1-F Ground
    A110P1-E Ground
    A110P1-J Ground

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  12. Disconnect ACPC connector A54P4.
  13. Perform wiring checks (open circuit = failure) between A109P2 and A54P4 as follow:

    From To Result
    A109P2-49 A54P4-E
    A109P2-57 A54P4-F
    A109P2-63 A54P4-G
    A109P2-62 A54P4-H

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  14. Perform wiring checks (closed circuit = failure) between A109P2 and ground as follow:

    From To Result
    A109P2-49 Ground
    A109P2-57 Ground
    A109P2-63 Ground

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  15. Get access to the ACPC bottom section.
  16. Perform continuity checks (open circuit = failure) between APU GEN and K1 as follow:

    From To Result
    A110P1-T1 K1-C1
    A110P1-T2 K1-B1
    A110P1-T3 K1-A1

    1. If there is continuity, go to step 18.
    2. If there is no continuity, continue with next step.

  17. Perform wiring checks (including inside ACPC) between APU GEN and K1 as follow:

    From To Result
    A110P1-T1 K1-C1
    A110P1-T2 K1-B1
    A110P1-T3 K1-A1

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.
      NOTE: Call Bombardier for decision to repair ACPC wiring or replace ACPC.

  18. Perform wiring checks (closed circuit = failure) between APU GEN (A110P1) and ground as follow:

    From To Result
    A110P1-T1 Ground
    A110P1-T2 Ground
    A110P1-T3 Ground

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  19. On current transducer 5 (LCTA 5), disconnect connector PL5.
  20. Perform continuity checks (open circuit = failure) in ACPC between connectors A54P4 and PL5 as follow:

    From To Result
    A54P4-E PL5-1
    A54P4-F PL5-2
    A54P4-G PL5-3
    A54P4-H PL5-4

    1. If there is no continuity, go to step 27.
    2. If there is continuity, continue with next step.

  21. Perform continuity checks (closed circuit = failure) in ACPC connectors between A54P4 and ground as follow:

    From To Result
    A54P4-E Ground
    A54P4-F Ground
    A54P4-G Ground

    1. If there is continuity, go to step 27.
    2. If there is no continuity, continue with next step.

  22. Perform continuity checks (open circuit = failure) as follow:

    From To Result
    PL5-1 PL5-4
    PL5-2 PL5-4
    PL5-3 PL5-4

    1. If there is no continuity, go to step 24.
    2. If there is continuity, continue with next step.

  23. Perform continuity checks (short circuit = failure) as follow:

    From To Result
    JL1-1 Ground
    JL1-2 Ground
    JL1-3 Ground

    1. If there is no continuity, go to step 25.
    2. If there is continuity, continue with next step.

  24. Replace LCTA 5.

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

  25. Replace K1.

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

  26. Replace APU GEN.

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

  27. Replace ACPC.
  28. Do close out.

apu-gen-delta-current-faultgcu

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