DOC AIRBUS | TSM A320FNacelle Latch Doors Proximity Switch 1 Failed Closed on EIU-1
TASK 73-25-00-810-B47-A
Nacelle Latch Doors Proximity Switch 1 Failed Closed on EIU-1
1. Possible Causes
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Fault Confirmation
Subtask 73-25-00-710-586-A ** ON A/C NOT FOR ALL
Subtask 73-25-00-810-470-A ** ON A/C NOT FOR ALL
Subtask 73-25-00-860-192-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:36:52 UTC
Nacelle Latch Doors Proximity Switch 1 Failed Closed on EIU-1
1. Possible Causes
- EIU-1 [1KS1]
- FAN COWL LATCH PROXIMITY SENSOR HARNESS [4145KS]
- FAN COWL LATCH PROXIMITY SENSOR HARNESS [4146KS]
- HARNESS - LEFT TRAS [4131KS]
- aircraft harness
A. Fixtures, Tools, Test and Support Equipment
| REFERENCE | QTY | DESIGNATION |
|---|---|---|
| No specific | 1 | MULTIMETER - STANDARD |
| No specific | 1 | PLIERS - JAWED, SOFT |
| REFERENCE | DESIGNATION |
|---|---|
| AMM 71-13-00-010-802 | Opening of the Fan Cowl Doors |
| AMM 71-13-00-410-802 | Closing of the Fan Cowl Doors |
| AMM 71-13-00-710-802 | Operational test of the Fan Cowl Loss Prevention System |
| AMM 71-13-22-000-801 | Removal of the Fan Cowl Proximity Sensor Switches |
| AMM 71-13-22-400-801 | Installation of the Fan Cowl Proximity Sensor Switches |
| AMM 71-13-61-000-801 | Removal of the Fan Cowl Latch Proximity Sensor Harness (4146KS) |
| AMM 71-13-61-000-802 | Removal of the Pylon Fan Cowl Latch Proximity Sensor Harness (4145KS) |
| AMM 71-13-61-400-801 | Installation of the Fan Cowl Latch Proximity Sensor Harness (4146KS) |
| AMM 71-13-61-400-802 | Installation of the Fan Cowl Latch Proximity Sensor Harness (4145KS) |
| AMM 73-25-34-000-802 | Removal of the Engine Interface Unit (EIU) |
| AMM 73-25-34-400-802 | Installation of the Engine Interface Unit (EIU) |
| AMM 73-25-34-860-806 | Engine Interface Unit (EIU) DISCRETE INPUTS Menu Data Status |
| AWM 783609 |
Subtask 73-25-00-710-586-A ** ON A/C NOT FOR ALL
A. Do the operational test of the fan cowl loss prevention system AMM 71-13-00-710-802.
(1) Determine that forward fan cowl latch is faulty.
4. Fault Isolation(1) Determine that forward fan cowl latch is faulty.
Subtask 73-25-00-810-470-A ** ON A/C NOT FOR ALL
A. If there is confirmation of the fault:
(1) With the aircraft in same configuration as required in fan cowl loss prevention system test, check the status of the EIU-1 discrete input.
(a) Make sure that the forward fan cowl latch is correctly open.
(b) Check the status of the EIU-1 discrete input for LATCH DOOR MON SW1 AMM 73-25-34-860-806.
1 If the status of the discrete input is equal to 0:
a Replace EIU-1 [1KS1] AMM 73-25-34-000-802 and AMM 73-25-34-400-802.
(2) If the status of the discrete input is equal to 1, do a visual inspection of nacelle connectors and harnesses:
(a) Open the fan cowl doors on ENG 1 AMM 71-13-00-010-802.
(b) At proximity switches of the forward fan cowl latch, use a PLIERS - JAWED, SOFT to disconnect connector(s) (4231KS-A) and (4056VC-A) and disconnect connector (443VC1-A) at pylon junction box AMM 71-13-61-000-802 and AMM 71-13-61-000-801.
(c) Examine the connectors and harnesses:
1 Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face. Replace parts as necessary.
2 Inspect the harnesses (4145KS) and (4146KS) for chafing. If you find damage:
a Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4145KS] AMM 71-13-61-000-802, and/or
b Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4146KS] AMM 71-13-61-000-801.
3 Reconnect the electrical connectors.
4 Do the test given in Para. 3.
(d) If you find no damage or if the fault continues:
1 Replace HARNESS - LEFT TRAS [4131KS] AMM 71-13-22-000-801 and AMM 71-13-22-400-801.
2 Do the test given in Para. 3.
(3) If the fault continues, use a MULTIMETER - STANDARD to do a check of nacelle wiring:
(a) At proximity switches of the forward fan cowl latch, disconnect connector (4231KS-A) and disconnect connector (443VC1-A) at pylon junction box AMM 71-13-61-000-802 and AMM 71-13-61-000-801.
(b) Look for wire-to-wire shorts.
Table 1: Forward Latch Connector Contacts
(c) If wiring is not OK, disconnect connector 4056VC-A.
(d) Look for wire-to-wire shorts.
Table 2: Forward Latch Connector Contacts
(e) If wiring is not OK:
1 Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4145KS] AMM 71-13-61-000-802 and AMM 71-13-61-400-802.
(f) If wiring is OK:
1 Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4146KS] AMM 71-13-61-000-801 and AMM 71-13-61-400-801.
(g) Do the test given in Para. 3.
(4) If there is no damage on nacelle harnesses or if the fault continues, do a check of aircraft wiring AWM 783609.
(a) Remove EIU-1 (1KS1) AMM 73-25-34-000-802 and disconnect connector 443VC-A at pylon junction box of ENG 1.
(b) Look for wire-to-wire shorts.
Table 3: Forward Latch Connector Contacts
(c) Repair or replace aircraft harness AWM 783609.
(d) Install EIU-1 (1KS1) AMM 73-25-34-400-802 and connect connector (443VC-A) at pylon junction box of ENG 1.
(e) Do the test given in Para. 3.
5. Close-up(1) With the aircraft in same configuration as required in fan cowl loss prevention system test, check the status of the EIU-1 discrete input.
(a) Make sure that the forward fan cowl latch is correctly open.
(b) Check the status of the EIU-1 discrete input for LATCH DOOR MON SW1 AMM 73-25-34-860-806.
1 If the status of the discrete input is equal to 0:
a Replace EIU-1 [1KS1] AMM 73-25-34-000-802 and AMM 73-25-34-400-802.
(2) If the status of the discrete input is equal to 1, do a visual inspection of nacelle connectors and harnesses:
(a) Open the fan cowl doors on ENG 1 AMM 71-13-00-010-802.
(b) At proximity switches of the forward fan cowl latch, use a PLIERS - JAWED, SOFT to disconnect connector(s) (4231KS-A) and (4056VC-A) and disconnect connector (443VC1-A) at pylon junction box AMM 71-13-61-000-802 and AMM 71-13-61-000-801.
(c) Examine the connectors and harnesses:
1 Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face. Replace parts as necessary.
2 Inspect the harnesses (4145KS) and (4146KS) for chafing. If you find damage:
a Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4145KS] AMM 71-13-61-000-802, and/or
b Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4146KS] AMM 71-13-61-000-801.
3 Reconnect the electrical connectors.
4 Do the test given in Para. 3.
(d) If you find no damage or if the fault continues:
1 Replace HARNESS - LEFT TRAS [4131KS] AMM 71-13-22-000-801 and AMM 71-13-22-400-801.
2 Do the test given in Para. 3.
(3) If the fault continues, use a MULTIMETER - STANDARD to do a check of nacelle wiring:
(a) At proximity switches of the forward fan cowl latch, disconnect connector (4231KS-A) and disconnect connector (443VC1-A) at pylon junction box AMM 71-13-61-000-802 and AMM 71-13-61-000-801.
(b) Look for wire-to-wire shorts.
Table 1: Forward Latch Connector Contacts
| 4231KS-A Connector Pins | 443VC-A Connector Pins |
|---|---|
| 2 | 21 |
| 5 | 1 |
| 3 | 10 |
(d) Look for wire-to-wire shorts.
Table 2: Forward Latch Connector Contacts
| 4056KS-A Connector Pins | 443VC-A Connector Pins |
|---|---|
| 1 | 21 |
| 6 | 1 |
| 5 | 10 |
1 Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4145KS] AMM 71-13-61-000-802 and AMM 71-13-61-400-802.
(f) If wiring is OK:
1 Replace FAN COWL LATCH PROXIMITY SENSOR HARNESS [4146KS] AMM 71-13-61-000-801 and AMM 71-13-61-400-801.
(g) Do the test given in Para. 3.
(4) If there is no damage on nacelle harnesses or if the fault continues, do a check of aircraft wiring AWM 783609.
(a) Remove EIU-1 (1KS1) AMM 73-25-34-000-802 and disconnect connector 443VC-A at pylon junction box of ENG 1.
(b) Look for wire-to-wire shorts.
Table 3: Forward Latch Connector Contacts
| (1KS1) Connector AA Pins | 452VT1 Terminal Block Pins | 443VC1 Connector Pins |
|---|---|---|
| C | 21 | |
| 9H | 1 | |
| 10 at ground |
(d) Install EIU-1 (1KS1) AMM 73-25-34-400-802 and connect connector (443VC-A) at pylon junction box of ENG 1.
(e) Do the test given in Para. 3.
Subtask 73-25-00-860-192-A ** ON A/C NOT FOR ALL
A. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the fan cowl doors AMM 71-13-00-410-802.
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the fan cowl doors AMM 71-13-00-410-802.