Fault Message:

ACPC EXT A/D CNVTR CARD - A9 RS422

Fault Code:

2451501ACP

Associated CAS:

ELEC SYS FAULT
(Advisory)

AC Power Center (ACPC) External A/D Converter Card has detected a problem on the RS422 communication bus between itself and Generator Control Unit (GCU) 2 or the Auxiliary Power Unit Generator Control Unit (APU GCU).

• Generator Control Unit (GCU) 2 (A57)
• Auxiliary Power Unit Generator Control Unit (APU GCU) (A109)
• AC Power Center (ACPC) (A54)
• AC Power Center (ACPC) External A/D Converter Card
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW700-45-0065 - CAIMS Nuisance Fault Messages

Forum Articles/Infoservice/Newsletter: None

NOTE: If this CAIMS message is observed at a time when the aircraft had been in the ground service mode, the message can be considered as nuisance.

• The messages is caused by a loss of communication between the Generator Control Units (GCU) and ACPC card. This loss of communication occurs as a normal function of the electrical system once the aircraft is in Ground Service mode. The battery bus is shed, which removes power from the GCU, resulting in loss of communication between the GCUs and ACPC cards.
• Take note that there will be no indication in the cockpit as it is 'black' when in Ground Service mode.

1. Swap GCU 2 with GCU 1. Is the fault resolved?

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

2. Swap the APU GCU with GCU 1. Is the fault resolved?

   1. If YES, replace APU GCU and do close out.
   2. If NO, continue with next step.

3. Check for power (28 VDC) at A109P1-N on the APU GCU.

   1. If 28 VDC is present, continue with next step.
   2. If 28 VDC is missing, investigate the wiring and/or power source (SPDA 2) and repair/replace if required. Refer to 246OBS003 - SPDA INOP SYSTEM.

4. Disconnect GCU 2 connector A57P2. Get access to ACPC logical assembly and remove Ext. A/D converter card. Perform a continuity check as follows:

From	To	Result
A57P2-9	Ground
A57P2-15	Ground

1. If there is continuity, go to step 6.
2. If there is no continuity, continue with next step.

5. Perform a continuity check as follows:

   From	To	Result
   A57P2-9	P520C-18
   A57P2-15	P520C-19

   1. If there is continuity, leave the A/D converter card removed and go to step 8.
   2. If there is no continuity, go to step 7.

6. Disconnect ACPC connector A54P7. Perform a continuity check as follows:

   From	To	Result
   A57P2-9	Ground
   A57P2-15	Ground

   1. If there is continuity, repair defective wiring as required and do close out.
   2. If there is no continuity, go to step 12.

7. Disconnect ACPC connector A54P7. Perform a continuity check as follows:

   From	To	Result
   A57P2-9	A54P7-a
   A57P2-15	A54P7-b

   1. If there is continuity, go to step 12.
   2. If there is no continuity, repair defective wiring as required and do close out.

8. Disconnect APU GCU connector A109P2. Perform a continuity check as follows:

   From	To	Result
   A109P2-9	Ground
   A109P2-15	Ground

   1. If there is continuity, continue with next step.
   2. If there is no continuity, go to step 10.

9. Disconnect ACPC connector A54P4 and perform a continuity check as follows:

   From	To	Result
   A109P2-9	Ground
   A109P2-15	Ground

   1. If there is continuity, repair defective wiring as required and do close out.
   2. If there is no continuity, go to step 12.

10. Perform a continuity check as follows:

    From	To	Result
    A109P2-9	P520B-28
    A109P2-15	P520B-29

    1. If there is continuity, replace A/D converter card and do close out.
    2. If there is no continuity, continue with next step.

11. Disconnect ACPC connector A54P4. Perform a continuity check as follows:

    From	To	Result
    A109P2-9	A54P4-a
    A109P2-15	A54P4-b

    1. If there is continuity, continue with next step.
    2. If there is no continuity, repair defective wiring as required and do close out.

12. Replace ACPC.
13. Do close out.