02/10/25
Message Overview:
Message Name:
GCU4 [VOLTAGE REGULATOR LOW]
Message Code:
2424107LPS
Associated CAS:
| Reporting LRU: | Generator Control Unit (GCU) 4 |
| System Description: | 24-21-00 - Primary AC Power Supply |
| Schematic Diagram: | SSM 24-21-00-101 - Primary AC Power Supply System [ Global Express ] [ G5000 ] [ Global XRS ] |
| Wiring Diagram: | 24-21-04 - AC Power Generation and Control No 4 System [ Global Express ] [ G5000 ] [ Global XRS ] |
Message Description:
Generator Control Unit (GCU) 4 has detected a voltage regulator low failure, consequently resulting in a Generator 4 to tripped off-line or not come on-line.
Possible Causes:
- Generator Control Unit (GCU) 4 (A59)
- Variable Frequency Generator (VFG) 4 (G4)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None
Flight Operation Notifications Manual (FONM): None
NOTES:
- 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:
| Standard Aircraft Configuration for Maintenance | [ G5000 ] [ Global Express ] [ Global XRS ] AMM12-00-00-867-801 |
| Aircraft Walkaround (for Maintenance) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM12-00-00-867-802 |
| Connect Electrical Power to the Aircraft | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-00-00-861-801 |
| Remove the Electrical Power from the Aircraft | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-00-00-861-802 |
| Electrical/Electronic Safety Precautions | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-00-00-910-801 |
| Electrostatic Discharge Safety Precautions | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-00-00-910-802 |
| Removal of the Variable Frequency Generators (VFG) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-21-01-000-801 |
| Installation of the Variable Frequency Generators (VFG) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-21-01-400-801 |
| Operational Test of the Variable Frequency Generators (VFG) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-21-01-710-801 |
| Removal of the Generator Control Units (GCU) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-24-01-000-801 |
| Installation of the Generator Control Units (GCU) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-24-01-400-801 |
| Operational Test of the Generator Control Units (GCU) | [ G5000 ] [ Global Express ] [ Global XRS ] AMM24-24-01-710-801 |
| Access to Active Faults | [ G5000 ] [ Global Express ] [ Global XRS ] AMM45-45-00-970-802 |
| Access to System Diagnostics | [ G5000 ] [ Global Express ] [ Global XRS ] AMM45-45-00-970-804 |
Troubleshooting Recommendations:
- Remove power from the A/C completely. Apply power back on the A/C. Is the fault still present?
- If NO, do close out.
- If YES, continue with next step.
- Interchange GCU 4 with GCU 3. Is the fault still present?
- If NO, replace GCU 4 and do close out.
- If YES, continue with next step.
- Disconnect VFG 4 connector G4P1, ACPC connector A54P2 and GCU 4 connector A59P1. Perform a continuity check as follows:
From To Result A59P1-J Ground A59P1-K Ground A59P1-A Ground A59P1-B Ground A59P1-C Ground - If there is continuity, repair defective wiring as required and do close out.
- If there is no continuity, continue with next step.
- Perform a continuity check as follows:
From To Result A59P1-J G4P1-H A59P1-K G4P1-B A59P1-A A54P2-A A59P1-B A54P2-B A59P1-C A54P2-C - If there is no continuity, repair defective wiring as required and do close out.
- If there is continuity, continue with next step.
- At VFG, disconnect G terminal.
- Perform a continuity check on aircraft wiring side as follow:
From To Result G4-G Ground - If there is no continuity, repair defective wiring as required and do close out.
- If there is continuity, continue with next step.
- Replace VFG 4.
- Do close out.