DOC AIRBUS | TSM A320FLeft Track Lock Proximity Switch Signal Failure on Channel A
TASK 78-31-00-810-955-A
Left Track Lock Proximity Switch Signal Failure on Channel A
1. Possible Causes
A. Referenced Information
3. Fault Confirmation
Subtask 78-31-00-710-270-A ** ON A/C NOT FOR ALL
Subtask 78-31-00-860-064-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:38:14 UTC
Left Track Lock Proximity Switch Signal Failure on Channel A
1. Possible Causes
- TERTIARY LOCK UNIT-TRAS, L [3021KM]
- HARNESS - LEFT TRAS [4131KS]
- HARNESS - PYLON T/R [4130KS]
- EEC WIRING HARNESS WF06 [4089KS]
- PROX SENSOR-L T/R LOWER TERTIARY LOCK, CHAN A [4038KS]
[4000KS]
A. Referenced Information
| REFERENCE | DESIGNATION |
|---|---|
| TSM TASK 71-00-00-810-843-A | Nacelle Component and Harness Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults |
| AMM 71-13-00-010-802 | Opening of the Fan Cowl Doors |
| AMM 71-13-00-410-802 | Closing of the Fan Cowl Doors |
| AWM 715135 | |
| AWM 715178 | |
| AMM 73-21-01-000-801 | Removal of the Electronic Engine Control (EEC) |
| AMM 73-21-01-400-801 | Installation of the Electronic Engine Control (EEC) |
| AMM 73-21-66-000-802 | Removal of the Electronic Engine Control (EEC) Wiring Harness (WF06) |
| AMM 73-21-66-400-802 | Installation of the Electronic Engine Control (EEC) Wiring Harness (WF06) |
| AMM 78-31-00-210-802 | General Visual Inspection (GVI) of the Proximity Sensor Targets |
| AMM 78-31-00-710-805 | Operational Test of Thrust Reverser with MCDU |
| AMM 78-31-61-000-811 | Removal of the Left TRAS Monitoring Harness |
| AMM 78-31-61-000-813 | Removal of the Pylon TRAS Monitoring Harness |
| AMM 78-31-61-400-811 | Installation of the Left TRAS Monitoring Harness |
| AMM 78-31-61-400-813 | Installation of the Pylon TRAS Monitoring Harness |
| AMM 78-36-00-010-802 | Opening of the Thrust Reverser Cowl-Doors |
| AMM 78-36-00-410-802 | Closing of the Thrust Reverser Cowl-Doors |
| AMM 78-37-01-000-801 | Removal of the Thrust Reverser Actuator System (TRAS) Track Lock |
| AMM 78-37-01-400-801 | Installation of the Thrust Reverser Actuator System (TRAS) Track Lock |
| AMM 78-37-20-000-801 | Removal of the TRAS Track Lock Proximity Sensors |
| AMM 78-37-20-400-801 | Installation of the TRAS Track Lock Proximity Sensors |
Subtask 78-31-00-710-270-A ** ON A/C NOT FOR ALL
A. Do the operational test of the thrust reverser with the MCDU to confirm this fault AMM 78-31-00-710-805.
(1) If the maintenance message does not come back, troubleshoot as described in the nacelle component and harness troubleshooting procedure for guidance troubleshooting intermittent faults (Ref. TSM TASK 71-00-00-810-843).
(a) Monitor the engine reoccurring maintenance message.
(2) If the maintenance message comes back (hard fault), go to the Para. Fault Isolation.
4. Fault Isolation(1) If the maintenance message does not come back, troubleshoot as described in the nacelle component and harness troubleshooting procedure for guidance troubleshooting intermittent faults (Ref. TSM TASK 71-00-00-810-843).
(a) Monitor the engine reoccurring maintenance message.
(2) If the maintenance message comes back (hard fault), go to the Para. Fault Isolation.
WARNING:
BE CAREFUL WHEN YOU DO WORK ON THE ENGINE AFTER SHUTDOWN. THE ENGINE CAN STAY HOT FOR A LONG TIME. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.
CAUTION:
MAKE SURE YOU REMOVE ELECTRICAL POWER FROM THE EEC BEFORE YOU REMOVE THE ELECTRICAL CONNECTORS. IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE EEC CAN OCCUR.
Subtask 78-31-00-810-299-A ** ON A/C NOT FOR ALL A. If there is confirmation of the fault:
(1) Get access to left track lock and EEC:
(a) Open the fan cowl doors AMM 71-13-00-010-802.
(b) Open the left thrust reverser cowl door AMM 78-36-00-010-802.
(c) Remove the track lock cover AMM 78-37-01-000-801.
(2) On track lock, at proximity sensor (4038KS), make sure that the target is not missing and do a visual inspection of the target for bend, breakage or damage AMM 78-31-00-210-802.
(a) If you find a bend, breakage or other damage, or if the target is missing:
1 Replace TERTIARY LOCK UNIT-TRAS, L [3021KM] AMM 78-37-01-000-801 and AMM 78-37-01-400-801.
2 Do the test given in Para. 3.
(3) If you find no damage or if the fault continues:
(a) Check for the correct engagement of connector (4038KS-A) and proximity sensor (4038KS):
1 Repair as necessary.
2 Do the test given in Para. 3.
(4) If check is OK or if the fault continues, disconnect connector (4038KS-A) and do a visual inspection of the connector for bent pins, contamination or corrosion or other signs of damage.
(a) If you find damage, replace HARNESS - LEFT TRAS [4131KS] AMM 78-31-61-000-811 and AMM 78-31-61-400-811.
(5) If you find no damage or if the fault continues, disconnect connector (4052VC) AWM 715178.
(a) Do a visual inspection of the connectors for bent pins, contamination or corrosion or other signs of damage.
(b) Do a continuity check (less than 5 ohms) between the pins of connectors (4038KS-A) and (4052VC) as follows:
(d) If you find damage, replace HARNESS - LEFT TRAS [4131KS] AMM 78-31-61-000-811 and AMM 78-31-61-400-811.
1 Reconnect all connectors.
2 Do the test given in Para. 3.
(6) If you find no damage, or if the fault continues, disconnect connectors (491VC-A) and (4052VC-A) AWM 715178.
(a) Do a visual inspection of the connectors for bent pins, contamination or corrosion or other signs of damage.
(b) Do a continuity check (less than 5 ohms) between the pins of connectors (4052VC-A) and (491VC) as follows:
(d) If you find a fault:
1 Replace HARNESS - PYLON T/R [4130KS] AMM 78-31-61-000-813 and AMM 78-31-61-400-813.
2 Reconnect all connectors.
3 Do the test given in Para. 3.
(7) If your find no damage or if the fault continues, disconnect connectors (491VC-A) and P7 from EEC AWM 715135.
(a) Do a visual inspection of the connector for bent pins, contamination or corrosion or other signs of damage.
(b) Do a continuity check (less than 5 ohms) between the pins of connectors P7 and (491VC-A) as follows:
(d) If you find a fault:
1 Replace EEC WIRING HARNESS WF06 [4089KS] AMM 73-21-66-000-802 and AMM 73-21-66-400-802.
2 Reconnect all connectors.
3 Do the test given in Para. 3.
(8) If you find no damage or if the fault continues:
(a) Replace PROX SENSOR-L T/R LOWER TERTIARY LOCK, CHAN A [4038KS] AMM 78-37-20-000-801 and AMM 78-37-20-400-801.
(b) Do the test given in Para. 3.
(9) If you find no fault or if the fault continues, replace
5. Close-up(1) Get access to left track lock and EEC:
(a) Open the fan cowl doors AMM 71-13-00-010-802.
(b) Open the left thrust reverser cowl door AMM 78-36-00-010-802.
(c) Remove the track lock cover AMM 78-37-01-000-801.
(2) On track lock, at proximity sensor (4038KS), make sure that the target is not missing and do a visual inspection of the target for bend, breakage or damage AMM 78-31-00-210-802.
(a) If you find a bend, breakage or other damage, or if the target is missing:
1 Replace TERTIARY LOCK UNIT-TRAS, L [3021KM] AMM 78-37-01-000-801 and AMM 78-37-01-400-801.
2 Do the test given in Para. 3.
(3) If you find no damage or if the fault continues:
(a) Check for the correct engagement of connector (4038KS-A) and proximity sensor (4038KS):
1 Repair as necessary.
2 Do the test given in Para. 3.
(4) If check is OK or if the fault continues, disconnect connector (4038KS-A) and do a visual inspection of the connector for bent pins, contamination or corrosion or other signs of damage.
(a) If you find damage, replace HARNESS - LEFT TRAS [4131KS] AMM 78-31-61-000-811 and AMM 78-31-61-400-811.
(5) If you find no damage or if the fault continues, disconnect connector (4052VC) AWM 715178.
(a) Do a visual inspection of the connectors for bent pins, contamination or corrosion or other signs of damage.
(b) Do a continuity check (less than 5 ohms) between the pins of connectors (4038KS-A) and (4052VC) as follows:
- Pin 2 and pin 8
- Pin 5 and pin 19
- Pin 3 and pin 20.
(d) If you find damage, replace HARNESS - LEFT TRAS [4131KS] AMM 78-31-61-000-811 and AMM 78-31-61-400-811.
1 Reconnect all connectors.
2 Do the test given in Para. 3.
(6) If you find no damage, or if the fault continues, disconnect connectors (491VC-A) and (4052VC-A) AWM 715178.
(a) Do a visual inspection of the connectors for bent pins, contamination or corrosion or other signs of damage.
(b) Do a continuity check (less than 5 ohms) between the pins of connectors (4052VC-A) and (491VC) as follows:
- Pin 8 and pin 10
- Pin 19 and pin 25
- Pin 20 and pin 26.
(d) If you find a fault:
1 Replace HARNESS - PYLON T/R [4130KS] AMM 78-31-61-000-813 and AMM 78-31-61-400-813.
2 Reconnect all connectors.
3 Do the test given in Para. 3.
(7) If your find no damage or if the fault continues, disconnect connectors (491VC-A) and P7 from EEC AWM 715135.
(a) Do a visual inspection of the connector for bent pins, contamination or corrosion or other signs of damage.
(b) Do a continuity check (less than 5 ohms) between the pins of connectors P7 and (491VC-A) as follows:
- Pin FF and pin 10
- Pin EE and pin 25
- Pin DD and pin 26.
(d) If you find a fault:
1 Replace EEC WIRING HARNESS WF06 [4089KS] AMM 73-21-66-000-802 and AMM 73-21-66-400-802.
2 Reconnect all connectors.
3 Do the test given in Para. 3.
(8) If you find no damage or if the fault continues:
(a) Replace PROX SENSOR-L T/R LOWER TERTIARY LOCK, CHAN A [4038KS] AMM 78-37-20-000-801 and AMM 78-37-20-400-801.
(b) Do the test given in Para. 3.
(9) If you find no fault or if the fault continues, replace
Subtask 78-31-00-860-064-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.
(a) Install the track lock cover AMM 78-37-01-400-801.
(b) Close the left thrust reverser cowl door AMM 78-36-00-410-802.
(c) 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.
(a) Install the track lock cover AMM 78-37-01-400-801.
(b) Close the left thrust reverser cowl door AMM 78-36-00-410-802.
(c) Close the fan cowl doors AMM 71-13-00-410-802.