Fault Message:

POS VS CMD-INLET DOOR LIN ACTR/XDCR

Fault Code:

4960321APU

Associated CAS:

APU DOOR FAIL
(Caution)

Auxiliary Power Unit (APU) Air Inlet Door position differs from door command by more than 5 degrees for 10 seconds after the door is commanded open.

• Linear Actuator (A199)
• Inlet-Door Rotary Transducer (MT5)
• Full-Authority Digital Engine-Controller (FADEC) (A108)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

APU door position digital readout on the EICAS STATUS PAGE will appear in amber when the door position does not agree with the command from the FADEC.

1. Visually check door position and inspect air inlet door for blockage or damage.

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

2. Re-rack FADEC.

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

3. Inspect the linear actuator (A199) and its connector for damage, FOD and contamination,

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

4. Inspect the inlet door position rotary transducer and its connector for damage, FOD and contamination.

   1. If there is a damage, repair or replace as required and do close out.
   2. If there is no damage, continue with next step.

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

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

6. Perform a continuity check between the linear actuator connector (A199P1) and ground shell as follows:

   From	To	Expected Result	Result
   A199P1-A	Ground	>1 megaohm
   A199P1-C	Ground	>1 megaohm

   1. If the resistance check is not as mentioned above, repair defective wiring as required and do close out.
   2. If the resistance check is as mentioned above, continue with next step.

7. Perform wiring checks between and inlet door actuator connector (A199P1) and connector P803.

   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.

8. Perform a continuity check between the linear actuator connector (A199P1) and ground shell as follows:

   From	To	Expected Result	Result
   A199P1-A	Ground	>1 megaohm
   A199P1-B	Ground	>1 megaohm
   A199P1-C	Ground	>1 megaohm
   A199P1-D	Ground	>1 megaohm

   1. If the resistance check is not as mentioned above, repair defective wiring as required and do close out.
   2. If the resistance check is as mentioned above, continue with next step.

9. Perform a continuity check between connector J803 and APU starter contactor assembly connector (A48P1) as follows:

   From	To	Expected Result	Result
   J803-L	A48P1-e	<3 ohms

   1. If the resistance check is not as mentioned above, repair defective wiring as required and do close out.
   2. If the resistance check is as mentioned above, continue with next step.

10. Perform a continuity check between connector J803 and FADEC tray connector (A108BP1) as follows:

    From	To	Expected Result	Result
    J803-E	A108BP1-C4	<3 ohms
    J803-F	A108BP1-D4	<3 ohms

    1. If the resistance check is not as mentioned above, repair defective wiring as required and do close out.
    2. If the resistance check is as mentioned above, continue with next step.

11. Perform a continuity check between connector J803 and grounded shell as follows:

    From	To	Expected Result	Result
    J803-E	Ground	>1 megaohm
    J803-F	Ground	>1 megaohm

    1. If the resistance check is not as mentioned above, repair defective wiring as required and do close out.
    2. If the resistance check is as mentioned above, continue with next step.

12. Replace Inlet Door Actuator.

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

13. Replace FADEC.
14. Do close out.