Fault Message:

ACPC/AC BUS 4 FAILED

Fault Code:

2451388ACP

Associated CAS:

ELEC SYS FAIL
Caution

The AC BUS 4 is not powered or reported faulty by the AC Power Center (ACPC).

• AC Power Center (ACPC) (A54)
• AC Power Center (ACPC) Contactor (K13)
• Generator Line Contactor (GLC) 4 (K13)
• Generator Transfer Contactor (GTC)
• Secondary Logic Card (SLC) 4
• Solid-State Power Controller (SSPC) 10
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Apply power to the aircraft in the configuration that the ACPC AC Bus 4 FAILED message is posted in CAIMS.
2. In the flight deck, access AC Synoptic page.

   1. If AC electrical power is not supplied by VFG 4, go to step 4.
   2. If AC electrical power is supplied by VFG 4, continue with next step.

3. Access ACPC Primary Subassembly. Perform a 115 VAC voltage check as follows:

   From	To	Result
   K13-A1	Ground
   K13-B1	Ground
   K13-C1	Ground

   1. If there is voltage, go to step 5.
   2. If there is no voltage, troubleshoot involved contactors upstream of K13, leading to VFG 4 output. Replace defective contactors as required and do close out.

4. Access ACPC Primary Sub-assembly. Perform a 115 VAC voltage check as follows:

   From	To	Result
   K13-A3	Ground
   K13-B3	Ground
   K13-C3	Ground

   1. If there is no voltage, troubleshoot the involved contactors upstream of K13, leading to the power source and do close out.
   2. If there is voltage, continue with next step.

5. Open the circuit breaker to all the loads that are fed by AC BUS 4. Verify if AC BUS 4 is now powered.

   1. If AC BUS 4 is now powered, push in one circuit breaker at a time to find what circuit or system is shorted.
   2. If AC BUS 4 is not powered, continue with next step.

6. Remove power from the aircraft. Remove SSPC 10. Verify if the AC BUS 2 is shorted to ground by performing a continuity check as follow:

   From	To	Result
   K13-A2	Ground
   K13-B2	Ground
   K13-C2	Ground

   1. If there is no continuity, replace contactor K13 and do close out.
   2. If there is continuity, troubleshoot the short inside the ACPC, you may have to replace the ACPC and continue with next step.

7. Is the AC BUS 4 FAILED CAIMS message still present?

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

8. Swap SSPC card 10 with SSPC card 11.

   1. If system checks are good, replace the SSPC card 10 and do close out.
   2. If fault remains, continue with next step.

9. Swap SLC 4 with SLC 1, 2 or 3.

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

10. Remove SSPC card 10. Perform a continuity check as follows:

    From	To	Result
    P420-2	K13-A2
    P420-5	K13-B2
    P420-8	K13-C2

    1. If there is no continuity, go to step 14.
    2. If there is continuity, continue with next step.

11. Remove SLC 4 and Perform a continuity check as follows:

    From	To	Result
    P420A-20	P410B-13
    P420B-20	P410C-13
    P420C-20	P410C-14

    1. If there is no continuity, go to step 14.
    2. If there is continuity, continue with next step.

12. Perform a continuity check as follows:

    From	To	Result
    P420A-20	Ground
    P420B-20	Ground
    P420C-20	Ground

    1. If there is continuity, go to step 14.
    2. If there is no continuity, continue with next step.

13. Inspect contacts for SLC 4 and SSPC 10 and make sure the cards are properly seated when re-installed.
14. Replace ACPC.
15. Do close out.