Message Name:

APU BATT VOLTAGE - AMP - TEMP INDICATION ERRONEOUS

The Auxiliary Power Unit (APU) Battery voltage, amperage and/or temperature indication on the DC synoptic page are erroneous.

• Auxiliary Power Unit Battery (A89)
• Auxiliary Power Unit Battery Charger (A90)
• AC Power Center (ACPC) (A54)
• AC Power Center (ACPC) External AC/DC Converter Card
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Use the PMAT to access CAIMS active or stored faults.

   1. If there are ATA 24 related faults present, troubleshoot these faults first and continue with next step.
   2. If no related ATA 24 faults are present, continue with next step.

2. Swap the APU BATT charger with the Avionic BATT charger.

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

3. Perform a continuity check between the APU BATT and the APU BATT charger as follows:

   From	To	Result
   A89P1-Y	A90P1-Y
   A89P1-K	A90P1-K
   A89P1-J	A90P1-J
   A89P1-H	A90P1-H
   A89P1-X	A90P1-X

   NOTE: Make sure there is no continuity to ground on the listed wires as well.

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

4. Access the ACPC logic assembly and replace the ACPC External AC/DC Converter Card.

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

5. Perform the ACPC logic card isolation procedure.

   1. If faulty ACPC card is found, replace card as required and do close out.
   2. If no cards are found faulty, continue with next step.

6. Replace the APU battery.

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

7. Replace ACPC.
8. Do close out.