Message Name:

APU NO CRANK

Message Code:

4960131APU

Associated CAS:

APU SHUTDOWN
(Advisory)

Auxiliary Power Unit (APU) protective shutdown. APU speed has not increased to 5% speed after one of the conditions that follows:

• After 12 seconds when the oil temperature is more than -10°F (-23.3°C)
• After 50 seconds when the oil temperature is less than -10°F (-23.3°C)

Inhibited during Take-Off and Landing.

• Auxiliary Power Unit (APU) Starter-Contactor Assembly (ASCA) (A48)
• Starter Motor (B55)
• De-prime valve (V1)
• Auxiliary Power Unit (APU) Full-Authority Digital Engine-Controller (FADEC) (A108)
• Auxiliary Power Unit (APU) (AP7)
• Associated Wiring

Advisory Wire/Service Bulletin:

• Honeywell Service Bulletin (SIL-APU-98) - APU Seizure Due to Compressor Shroud Corrosion

Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

1. Get access to the active faults' messages in CAIMS.

   1. If any APU related fault messages are shown during the APU FADEC 'APU BITE check' before an APU start up, troubleshoot them first and continue with next step.
   2. If no APU related fault messages are shown, check in the history of recent fault messages, relating to the APU.
   3. If fault remains or if no APU fault is active and the APU SHUTDOWN
      (Advisory) is still shown on EICAS display, continue with next step.

2. Perform a visual check the engine branched wiring-harness for bare wiring, kinks, worn areas and other damage (WM 49-12).

   1. If damages are found, repair as required and do close out.
   2. If damages are not found, continue with next step.

3. Check for 28 VDC on receptacle T5 on the APU Starter-Contactor Assembly (ASCA).
   NOTE: This step must be performed during the start cycle.

   1. If there is 28 VDC (K2 Start Contractor is closed), go to step 5.
   2. If there is no voltage, continue with next step.

4. Replace the APU Starter-Contactor Assembly (ASCA).
   NOTE: If starter motor not disengaged, starter motor remains energized. FADEC can not detect a start contactor that failed to de-energize. This may be caused by a defective ASCA relay (closed position).

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

5. Perform wiring checks between APU Starter Motor B55 (-) negative and (+) positive terminals, continuity should be less than one ohm.

   1. If there is continuity, go to step 7.
   2. If there is no continuity, continue with next step.

6. Replace APU Starter Motor B55.

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

7. Verify that not all APU FADEC data is missing.

   1. If all data are present, go to step 9.
   2. If all data are missing, continue with next step.

8. Check APU firewall connector J802 from APU FADEC.

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

9. Re-rack APU FADEC and verify condition of connector A108AP1, A108BP1 and A108CP1 as well as APU mounting tray connectors for damage.

   1. If damages are found, repair as required and do close out.
   2. If damages are not found, continue with next step.

10. Perform wiring checks between FADEC connector (A108BP1) (Start Contactor Low Side Driver) and ASCA connector (A48P2) (APU Star Contactor).

    From	To	Result
    A108BP1-C5	A48P2-C

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

11. Perform wiring checks between FADEC connector (A108BP1) and de-prime valve connector (V1P1) as follow:

    From	To	Result
    A108BP1-116	V1P1-A
    A108BP1-117	V1P1-B

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

12. Perform a continuity check on the de-prime valve (V1) receptacle as follows:

    From	To	Expected Result	Result
    V1P1-A	V1P1-B	15 Ω - 25 Ω

    NOTE: De-prime valve is energized open when oil temp <-6.6°C.

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

13. Replace the de-prime valve.

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

14. Replace the APU FADEC.

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

15. Replace APU.
16. Do close out.