W DOC AIRBUS | TSM A320F

Failure of the Signal from the APU Control Relay to the GAPCU

TASK 24-20-00-810-947-A
Failure of the Signal from the APU Control Relay to the GAPCU

1. Possible Causes
  • GAPCU [24XG]
  • wiring
  • RELAY-APU AVAIL [6KD]
  • diode module 1162VD
  • RELAY-APU GLC AUX CTL [4XS]
2. Job Set-up Information
 A. Referenced Information
REFERENCE
DESIGNATION
ASM 242202
ASM 242302
AMM 24-41-00-740-002
Operational Check of the GAPCU via the CFDS
AMM 24-41-34-000-001
Removal of the Ground Power Control Unit (GPCU)
AMM 24-41-34-400-001
Installation of the Ground Power Control Unit (GPCU)
ASM 496101
3. Fault Confirmation
Subtask 24-20-00-740-086-A ** ON A/C NOT FOR ALL
A. Test
   (1) If the CFDS message APU CTL RLY (6KD)/ECB (59KD)/GAPCU (24XG) comes into view with CFDS messages related to the chapter 49 or to the ECB:
  • do the trouble shooting procedure related to the chapter 49 or ECB messages.
   (2) IF there are no chapter 49 or ECB messages, or if the fault continues after the trouble shooting:
     (a) If the BITE test gives the message TEST FAILED:
  • do the trouble shooting given in Para 4.A.
     (b) If the BITE test gives the message TEST PASSED:
  • do the trouble shooting given in Para 4.B.
4. Fault Isolation
Subtask 24-20-00-810-176-A ** ON A/C NOT FOR ALL
A. If the BITE test gives the message TEST FAILED:
  • push the line key adjacent to the TEST FAILED message.
   (1) If the maintenance message GAPCU (24XG) comes into view:
Subtask 24-20-00-865-055-A ** ON A/C NOT FOR ALL
B. Table of the circuit breakers used in this procedure:
PANELDESIGNATIONFINLOCATION
** ON A/C NOT FOR ALL
122VUELEC/GEN1/OFF/BTC1 SPLY5XUT28
Subtask 24-20-00-810-177-A ** ON A/C NOT FOR ALL
C. If the BITE test gives the message TEST PASSED:
  • Do a check of the wiring of the APU ready circuit ASM 496101, ASM 242302 and ASM 242202 between:
    . Pin AB/6J of the ECB (59KD) and pin A/X1 of the APU AVAIL relay (6KD)
    . Pin A/X2 of the APU AVAIL relay (6KD) and ground
    . Pin AA/7C of the GAPCU (24XG) and pin A/A1 of the APU AVAIL relay (6KD)
    . Pin A/A2 of the APU AVAIL relay (6KD) and pin A/37 of diode module 1162VD
    . Pin A/38 of diode module 1162VD and pin 2 of the ELEC/GEN1/OFF/BTC1 SPLY circuit breaker (5XU).
   (1) If the wiring is not correct:
  • Repair or replace as necessary.
   (2) If the wiring is correct:
  • Replace RELAY-APU AVAIL [6KD] .
   (3) If the fault continues:
  • Do a check for 28VDC at pin A/38 of diode module 1162VD.
     (a) If there is no 28VDC:
  • Do a check and repair the wiring between pin 2 of the ELEC/GEN1/OFF/BTC1 SPLY circuit breaker (5XU) and pin A/38 of diode module 1162VD ASM 242202.
     (b) If there is 28VDC:
Subtask 24-20-00-810-177-C ** ON A/C NOT FOR ALL
C. If the BITE test gives the message TEST PASSED:
  • Do a check of the wiring of the APU ready circuit, ASM 496101, ASM 242302 and ASM 242202, between:
    . Pin AB/10J of the GAPCU and pin C3 of the ELEC/APU GEN pushbutton switch (2XS)
    . Pin C1 of the ELEC/APU GEN pushbutton switch (2XS) and pin X1 of the APU-GLC auxiliary control-relay (4XS)
    . Pin X2 of the APU-GLC auxiliary control-relay (4XS) and the ground
    . Pin AB/10J of the GAPCU and pin A/1 of the APU-GLC auxiliary control-relay (4XS)
    . Pin AB/6J of the ECB (59KD) and pin A/X1 of the APU AVAIL relay (6KD)
    . Pin A/X2 of the APU AVAIL relay (6KD) and the ground
    . Pin AA/7C of the GAPCU (24XG) and pin A/A1 of the APU AVAIL relay (6KD)
    . Pin A/A2 of the APU AVAIL relay (6KD) and pin A/2 of the APU-GLC auxiliary control-relay (4XS)
    . Pin A/3 of the APU-GLC auxiliary control-relay (4XS) and pin 2 of the ELEC/GEN1/OFF/BTC1 SPLY circuit breaker (5XU).
   (1) If the wiring is not correct:
  • Repair it.
   (2) If the wiring is correct:
  • Replace the RELAY-APU AVAIL [6KD] .
   (3) If the fault continues:
  • Replace the RELAY-APU GLC AUX CTL [4XS] .
   (4) If the fault continues:
Subtask 24-20-00-740-087-A ** ON A/C NOT FOR ALL
D. Do the test given in Para. 3.
[Rev.8 from Aug 2018] 2026.04.04 04:26:26 UTC
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