DOC AIRBUS | TSM A320FAPU Detection Loop A and/or Loop B Fault
TASK 26-13-00-810-801-A
APU Detection Loop A and/or Loop B Fault
1. Possible Causes
2. Job Set-up Information
A. Referenced Information
3. Fault Confirmation
Subtask 26-13-00-710-050-A 4. Fault Isolation
Subtask 26-13-00-810-063-A
Subtask 26-13-00-860-050-A
[Rev.8 from Aug 2018]
2026.04.04 04:27:17 UTC
APU Detection Loop A and/or Loop B Fault
1. Possible Causes
2. Job Set-up Information
A. Referenced Information
| REFERENCE | DESIGNATION |
|---|---|
| AMM 26-13-00-710-002 | BITE Test of the APU Fire and Overheat Detection System |
| ASM 261301 | |
| AMM 26-13-15-000-001 | Removal of the Sensing Elements |
| AMM 26-13-15-400-001 | Installation of the Sensing Elements |
| AMM 26-13-34-000-001 | Removal of the APU Fire-Detection Unit (FDU) |
| AMM 26-13-34-400-001 | Installation of the APU Fire-Detection Unit (FDU) |
Subtask 26-13-00-710-050-A 4. Fault Isolation
Subtask 26-13-00-810-063-A
A. If the test gives a different maintenance message:
Subtask 26-13-00-810-050-A - Do the trouble shooting procedure related to the maintenance message.
B. If the test gives the maintenance message:
CHECK APU FIRE LOOP A and/or LOOP B
(a) Disconnect the electrical connector 21WG-A,
(b) On the responder of the DETECTOR-APU FIRE (LOOP A) [21WG] , make sure that the resistance between the
-pins A and B is less than 1 ohm,
-pins A and C are between 1455 ohms and 1545 ohms,
-pins A and D are between 1455 ohms and 1545 ohms,
-pins A and E are between 1455 ohms and 1545 ohms,
-pins B and C are between 1455 ohms and 1545 ohms,
-pins C and D is less than 1 ohm,
-pins D and E is less than 1 ohm,
-all of the pins and the responder of the DETECTOR-APU FIRE (LOOP A) [21WG] are more than 100 megohms.
(3) If the resistance value(s) is (are) in the specified limits:
(a) Connect the electrical connector 21WG-A,
(b) Replace the FDU-APU [13WG] AMM 26-13-34-000-001 and AMM 26-13-34-400-001.
(c) Do the test as given in the Para. 3.A.
Subtask 26-13-00-810-079-A CHECK APU FIRE LOOP A and/or LOOP B
- Do a visual inspection of the DETECTOR-APU FIRE (LOOP A) [21WG]
- Replace the DETECTOR-APU FIRE (LOOP A) [21WG] AMM 26-13-15-000-001 and AMM 26-13-15-400-001.
(a) Disconnect the electrical connector 21WG-A,
(b) On the responder of the DETECTOR-APU FIRE (LOOP A) [21WG] , make sure that the resistance between the
-pins A and B is less than 1 ohm,
-pins A and C are between 1455 ohms and 1545 ohms,
-pins A and D are between 1455 ohms and 1545 ohms,
-pins A and E are between 1455 ohms and 1545 ohms,
-pins B and C are between 1455 ohms and 1545 ohms,
-pins C and D is less than 1 ohm,
-pins D and E is less than 1 ohm,
-all of the pins and the responder of the DETECTOR-APU FIRE (LOOP A) [21WG] are more than 100 megohms.
(3) If the resistance value(s) is (are) in the specified limits:
(a) Connect the electrical connector 21WG-A,
(b) Replace the FDU-APU [13WG] AMM 26-13-34-000-001 and AMM 26-13-34-400-001.
(c) Do the test as given in the Para. 3.A.
C. If the fault continues:
(1) Do a check and repair the wiring between the:
FDU (13WG) connector A/K and DETECTOR (21WG) connector A/A,
FDU (13WG) connector A/J and DETECTOR (21WG) connector A/E ASM 261301.
(a) If the resistance value(s) is (are) not in the specified limits:
1 Replace DETECTOR-APU FIRE (LOOP A) [21WG] AMM 26-13-15-000-001 and AMM 26-13-15-400-001.
(b) Do the test as given in the Para. 3.A.
Subtask 26-13-00-810-053-A (1) Do a check and repair the wiring between the:
FDU (13WG) connector A/K and DETECTOR (21WG) connector A/A,
FDU (13WG) connector A/J and DETECTOR (21WG) connector A/E ASM 261301.
(a) If the resistance value(s) is (are) not in the specified limits:
1 Replace DETECTOR-APU FIRE (LOOP A) [21WG] AMM 26-13-15-000-001 and AMM 26-13-15-400-001.
(b) Do the test as given in the Para. 3.A.
D. If the test gives the maintenance message:
CHECK APU FIRE LOOP B
(a) Disconnect the electrical connector 22WG-A,
(b) On the responder of the DETECTOR-APU FIRE (LOOP B) [22WG] , make sure that the resistance between the
-pins A and B is less than 1 ohm,
-pins A and C are between 1455 ohms and 1545 ohms,
-pins A and D are between 1455 ohms and 1545 ohms,
-pins A and E are between 1455 ohms and 1545 ohms,
-pins B and C are between 1455 ohms and 1545 ohms,
-pins C and D is less than 1 ohm,
-pins D and E is less than 1 ohm,
-all of the pins and the responder of the DETECTOR-APU FIRE (LOOP B) [22WG] are more than 100 megohms.
(3) If the resistance value(s) is (are) in the specified limits:
(a) Connect the electrical connector 22WG-A,
(b) Replace the FDU-APU [13WG] AMM 26-13-34-000-001 and AMM 26-13-34-400-001.
(c) Do the test as given in the Para. 3.A.
Subtask 26-13-00-810-078-A CHECK APU FIRE LOOP B
- Do a visual inspection of the DETECTOR-APU FIRE (LOOP B) [22WG]
- Replace the DETECTOR-APU FIRE (LOOP B) [22WG] AMM 26-13-15-000-001 and AMM 26-13-15-400-001.
(a) Disconnect the electrical connector 22WG-A,
(b) On the responder of the DETECTOR-APU FIRE (LOOP B) [22WG] , make sure that the resistance between the
-pins A and B is less than 1 ohm,
-pins A and C are between 1455 ohms and 1545 ohms,
-pins A and D are between 1455 ohms and 1545 ohms,
-pins A and E are between 1455 ohms and 1545 ohms,
-pins B and C are between 1455 ohms and 1545 ohms,
-pins C and D is less than 1 ohm,
-pins D and E is less than 1 ohm,
-all of the pins and the responder of the DETECTOR-APU FIRE (LOOP B) [22WG] are more than 100 megohms.
(3) If the resistance value(s) is (are) in the specified limits:
(a) Connect the electrical connector 22WG-A,
(b) Replace the FDU-APU [13WG] AMM 26-13-34-000-001 and AMM 26-13-34-400-001.
(c) Do the test as given in the Para. 3.A.
E. If the fault continues:
(1) Do a check and repair the wiring between the:
FDU (13WG) connector B/K and DETECTOR (22WG) connector A/A.
FDU (13WG) connector B/J and DETECTOR (22WG) connector A/E ASM 26-13/01.
(a) If the resistance value(s) is (are) out of the specified limits:
Subtask 26-13-00-710-053-A (1) Do a check and repair the wiring between the:
FDU (13WG) connector B/K and DETECTOR (22WG) connector A/A.
FDU (13WG) connector B/J and DETECTOR (22WG) connector A/E ASM 26-13/01.
(a) If the resistance value(s) is (are) out of the specified limits:
- Replace the DETECTOR-APU FIRE (LOOP B) [22WG] AMM 26-13-15-000-001 and AMM 26-13-15-400-001.
F. Do the test as given in the Para. 3.A.
5. Close-upSubtask 26-13-00-860-050-A
A. Put the aircraft back to its initial configuration.