Fault Message:

APU BATT CHGR/APU BATT CHGR FEEDER

Fault Code:

2451381ACP

Associated CAS:

ELEC SYS FAIL
(Caution)

Fault message is triggered if External AC is AVAIL but there is no 28 V Transformer (T1)/Rectifier (CR1) output detected by the A/D converter card. The output voltage is measured at D4 on EM1 and D8 on EM2.

• Auxiliary Power Unit (APU) Battery Charger (A90)
• AC Power Center (ACPC) A/D Converter Card
• Thermal Circuit Breaker (CB-B7)
• AC Power Center (ACPC) (A54)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Make sure there are no AC BUS 2 related failure messages. If there is, troubleshoot AC BUS 2 first.
2. On the ACPC, verify the status of AC BUS 2 thermal circuit breaker CB-B7 “APU BATT CHGR”.

   1. If it is IN, go to step 4.
   2. If it is not IN, continue with next step.

3. Remove the APU BATT Charger. Set CB-B7 to IN. Did the thermal CB stay IN?

   1. If YES, replace APU BATT Charger and do close out.
   2. If NO, go to step 7.

4. Swap the APU BATT Charger with the Avionic BATT Charger and apply power to the A/C. Is the fault message still present?

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

5. Set CB-B7 to OUT. Access the ACPC Circuit Breaker assembly. Apply power to the A/C and perform a 115 VAC voltage check as follows:

   From	To	Result
   CB-B7-A1	Ground
   CB-B7-B1	Ground
   CB-B7-C1	Ground

   1. If there is no 115 VAC on all phases, troubleshoot the missing phase(s) from AC BUS 2 upstream of CB-B7 and do close out.
   2. If there is 115 VAC on all phases, continue with next step.

6. Set CB-B7 back to IN. Perform a 115 VAC voltage check as follows:

   From	To	Result
   CB-B7-A2	Ground
   CB-B7-B2	Ground
   CB-B7-C2	Ground

   1. If there is no 115 VAC on all phases, replace CB-B7 and do close out.
   2. If there is 115 VAC on all phases, continue with next step.

7. Remove power from the aircraft. Set CB-B7 to OUT. Disconnect the APU BATT Charger connector A90P1 and perform a continuity check as follows:

   From	To	Result
   CB-B7-A2	Ground
   CB-B7-B2	Ground
   CB-B7-C2	Ground

   1. If there is continuity, repair the defective aircraft wiring as required or replace ACPC if failure is in ACPC.
   2. If there is no continuity, continue with next step.

8. Perform a continuity check as follows:

   From	To	Result
   CB-B7-A2	A90P1-A
   CB-B7-B2	A90P1-B
   CB-B7-C2	A90P1-T

   1. If there is no continuity, repair defective aircraft wiring as required or replace ACPC if failure is in ACPC.
   2. If there is continuity, continue with next step.

9. Access the ACPC logic assembly. Remove the EXT A-D Converter card and perform a continuity check as follows:

   From	To	Result
   A90P1-M	Ground

   1. If there is continuity, repair defective aircraft wiring as required or replace ACPC if failure is in ACPC.
   2. If there is no continuity, continue with next step.

10. Perform a continuity check as follows:

    From	To	Result
    A90P1-M	P520C-9

    1. If there is no continuity, repair defective aircraft wiring as required or replace ACPC if failure is in ACPC.
    2. If there is continuity, continue with next step.

11. Replace the EXT A-D Converter Card in the ACPC.
12. Do close out.