W DOC AIRBUS | TSM A320F

Failure of the APU Feeder

TASK 24-20-00-810-841-A
Failure of the APU Feeder

1. Possible Causes
  • wiring
  • GCU-APU [1XS]
  • GEN-APU [8XS]
2. Job Set-up Information
 A. Referenced Information
REFERENCE
DESIGNATION
ASM 242301
AMM 24-23-34-000-001
Removal of the GCU-APU
AMM 24-23-34-400-001
Installation of the GCU-APU
AMM 24-23-51-000-001
Removal of the APU Generator
AMM 24-23-51-400-001
Installation of the APU Generator
AMM 24-41-00-861-002
Energize the Aircraft Electrical Circuits from the External Power
AMM 24-41-00-862-002
De-energize the Aircraft Electrical Circuits Supplied from the External Power
3. Fault Confirmation
Subtask 24-20-00-700-086-A ** ON A/C NOT FOR ALL
A. Test
Not applicable.
NOTE: As the APU GEN was set to OFF because of a true failure, the fault confirmation is not necessary.
4. Fault Isolation
Subtask 24-20-00-810-080-A ** ON A/C NOT FOR ALL
A. If the fault symptom is identified by the CFDS message CHECK GLC APU PIN D, E, F GCU APU PIN B1A, B2B, B3A and the upper ECAM DU warning : APU GEN FAULT:
  • do a check of the wiring :
    . between respectively the APU GCU pins B/1A, B/2B, B/3A and the APU GLC pins F, E, D
    . then between respectively the APU GEN terminals T/1, T/2, T/3 and the APU GLC pins F, E, D ASM 242301.
   (1) If the wiring is not correct:
  • repair it.
   (2) If the wiring is correct:
  • do an impedance check of the APU generator stator between terminals T/1, T/2, T/3 and terminal N.
NOTE: The normal impedance between each terminal and the neutral is 9.35 m.ohms plus or minus 1.25 m.ohms at 25°C.
     (a) If the impedance is in the specified limits:
  • make sure that the pins T/1, T/2, T/3 are electrically insulated from the case
  • then, after you have removed the neutral lead, do a check of the pins T/1, T/2 or T/3 for short to ground.
       1 if insulated:
NOTE: Do not remove the APU GCU before you do the other steps of the trouble shooting.
       2 If not insulated:
     (b) If the impedance is out of the specified limits:
Subtask 24-20-00-810-080-B ** ON A/C NOT FOR ALL
A. If the fault symptom is identified by the CFDS message CHECK GLC APU PIN D, E, F GCU APU PIN B1A, B2B, B3A and the upper ECAM DU warning APU GEN FAULT:
  • do a check of the wiring between:
    . respectively the APU GCU pins B/1A, B/2B, B/3A and the APU/EXT power contactor module (29XN) pins 7, 8, 9.
    . then respectively the APU GEN terminals T/1, T/2, T/3 and the APU/EXT power contactor module (29XN) pins 7, 8, 9 ASM 242301.
   (1) If the wiring is not correct:
  • repair it.
   (2) If the wiring is correct:
  • do an impedance check of the APU generator stator between terminals T/1, T/2, T/3 and terminal N.
NOTE: The normal impedance between each terminal and the neutral is 9.35 m.ohms plus or minus 1.25 m.ohms at 25°C.
     (a) If the impedance is in the specified limits:
  • make sure that the pins T/1, T/2, T/3 are electrically insulated from the case
  • then, after you have removed the neutral lead, do a check of the pins T/1, T/2 or T/3 for short to ground.
       1 If insulated:
NOTE: Do not remove the APU GCU before you do the other steps of the trouble shooting.
       2 If not insulated:
     (b) If the impedance is out of the specified limits:
Subtask 24-20-00-700-087-A ** ON A/C NOT FOR ALL
B. Make sure that the aircraft electrical circuits operate correctly in APU configuration.
   (1) Energize the aircraft electrical circuits from the APU AMM 24-41-00-861-002.
   (2) De-energize the aircraft electrical circuits from the APU AMM 24-41-00-862-002.
[Rev.8 from Aug 2018] 2026.04.04 04:26:13 UTC
"WTRUIB" 2025