Left Hand Lower Locking Actuator Proximity Switch Signal Failure on Channel B

TASK 78-31-00-810-960-A
Left Hand Lower Locking Actuator Proximity Switch Signal Failure on Channel B

1. Possible Causes

L LOWER ACTUATOR [3041KM2]
HARNESS - LEFT TRAS [4131KS]
HARNESS - PYLON T/R [4130KS]
EEC WIRING HARNESS WF07 [4093KS]
PROX SENSOR-L T/R LOWER PRIMARY LOCK, CHAN B [4042KS]
[4000KS]

2. Job Set-up Information
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 715136
AWM 715179
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 73-21-67-000-801	Removal of the Electronic Engine Control (EEC) Wiring Harness (WF07)
AMM 73-21-67-400-801	Installation of the Electronic Engine Control (EEC) Wiring Harness (WF07)
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 78-31-03-000-801	Removal of the TRAS Locking Actuator
AMM 78-31-03-400-801	Installation of the TRAS Locking Actuator
AMM 78-31-20-000-801	Removal of the TRAS Actuator Proximity-Sensors
AMM 78-31-20-400-801	Installation of the TRAS Actuator Proximity-Sensors
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

3. Fault Confirmation
Subtask 78-31-00-710-275-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

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 78-31-00-810-304-A ** ON A/C NOT FOR ALL

A. If there is confirmation of the fault:
(1) Get access to left hand lower locking actuator and EEC:
(a) Open the fan cowl doors AMM 71-13-00-010-802.
(2) On actuator, at proximity sensor (4042KS), 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 L LOWER ACTUATOR [3041KM2] AMM 78-31-03-000-801 and AMM 78-31-03-400-801.
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 (4042KS-A):
1 Repair as necessary.
2 Do the test given in Para. 3.
(4) If the check is OK or if the fault continues, disconnect connector (4042KS-A) and do a visual inspection of the connector for bent pins, contamination or corrosion or other signs of damage.
(a) If you fin 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 (4053VC-A) AWM 715179.
(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 (4042KS-A) and (4053VC) as follows:

Pin 2 and pin 6
Pin 5 and pin 16
Pin 3 and pin 17.

(c) Do a check of each wire for wire-to-wire, short circuit and short to ground.
(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 connector (494VC-A) AWM 715179.
(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 (4053VC-A) and (494VC) as follows:

Pin 6 and pin 3
Pin 16 and pin 2
Pin 17 and pin 11.

(c) Do a check of each wire for wire-to-wire, short circuit and short to ground.
(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 connector P7 from EEC AWM 715136.
(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 P8 and (494VC-A) as follows:

Pin w and pin 3
Pin x and pin 2
Pin e and pin 11.

(c) Do a check of each wire for wire-to-wire, short circuit and short to ground.
(d) If you find a fault:
1 Replace EEC WIRING HARNESS WF07 [4093KS] AMM 73-21-67-000-801 and AMM 73-21-67-400-801.
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 PRIMARY LOCK, CHAN B [4042KS] AMM 78-31-20-000-801 and AMM 78-31-20-400-801.
(b) Do the test given in Para. 3.
(9) If you find no fault or if the fault continues, replace [4000KS] AMM 73-21-01-000-801 and AMM 73-21-01-400-801.

5. Close-up
Subtask 78-31-00-860-069-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) Close the fan cowl doors AMM 71-13-00-410-802.

[Rev.8 from Aug 2018] 2026.04.04 04:38:15 UTC