DOC AIRBUS | TSM A320FPressure Proximity Switch Signal Failure on Channel A
TASK 78-31-00-810-944-A
Pressure Proximity Switch Signal Failure on Channel A
1. Possible Causes
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Fault Confirmation
Subtask 78-31-00-710-259-A ** ON A/C NOT FOR ALL
Subtask 78-31-00-860-053-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:41:32 UTC
Pressure Proximity Switch Signal Failure on Channel A
1. Possible Causes
- HCU-T/R, ENG1 [4310EG1]
- HCU-T/R, ENG2 [4310EG2]
- HARNESS-FAN, WF02 [4218KS]
- HCU PRESS SWITCH ENG 1A [102EG1]
- HCU PRESS SWITCH ENG 2A [102EG2]
[4000KS]
A. Fixtures, Tools, Test and Support Equipment
| REFERENCE | QTY | DESIGNATION |
|---|---|---|
| No specific | 1 | PLIERS - JAWED, SOFT |
| 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 | |
| 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 73-21-62-000-802 | Removal of the EEC Wiring Harness (WF02) |
| AMM 73-21-62-400-802 | Installation of the EEC Wiring Harness (WF02) |
| 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 78-31-01-000-801 | Removal of the TRAS Hydraulic Control Unit (HCU) |
| AMM 78-31-01-400-801 | Installation of the TRAS Hydraulic Control Unit (HCU) |
| AMM 78-31-21-000-801 | Removal of the Hydraulic Control Unit (HCU) Pressure Switch |
| AMM 78-31-21-400-801 | Installation of the Hydraulic Control Unit (HCU) Pressure Switch |
| FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1) | |
| AWM 783611 | |
| FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2) | |
| AWM 783612 | |
Subtask 78-31-00-710-259-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 78-31-00-810-288-A ** ON A/C NOT FOR ALL A. If there is confirmation of the fault:
(1) Get access to HCU, EEC and pylon junction box.
(a) Remove the access panel from the pylon to get access to the HCU:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
413AL
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
423AL
(b) Open the fan cowl-doors AMM 71-13-00-010-802.
(2) At HCU pressure switch (102EG), 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 HCU-T/R, ENG1 [4310EG1] or HCU-T/R, ENG2 [4310EG2] AMM 78-31-01-000-801 and AMM 78-31-01-400-801.
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 (102EG_A) and HCU pressure switch (102EG):
1 Repair as necessary.
2 Do the test given in Para. 3.
(4) If the check is OK or if the fault continues, use a PLIERS - JAWED, SOFT to disconnect connector (102EG-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 the pylon harness:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
AWM 783611
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
AWM 783612
(b) Reconnect connector (102EG-A).
(c) Do the test given in Para. 3.
(5) If you find no damage or if that fault continues, disconnect connectors (102EG-A) and P1 from the EEC (4000KS) AWM 715135.
(a) Do a continuity check (less than 5 ohms) between the pins of connectors P1 and (102EG-A) as follows:
(e) If you find a fault:
1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
2 Do the test given in Para. 3.
(f) If there is continuity:
1 Replace the pylon harness:
a FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
AWM 783611
b FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
AWM 783612
2 Reconnect all connectors.
3 Do the test given in Para. 3.
(6) If there is continuity between connectors P1 and (102EG-A) or if fault continues, disconnect connector (102EG-A) and do a visual inspection of the HCU pressure switch (102EG) for bent pins, contamination or corrosion, or other signs of damage.
(a) If you find damage, replace HCU PRESS SWITCH ENG 1A [102EG1] or HCU PRESS SWITCH ENG 2A [102EG2] AMM 78-31-21-000-801 and AMM 78-31-21-400-801.
(b) Do the test given in Para. 3.
(7) If you find no damage or if the fault continues, disconnect connector (102EG-A) and do a check for continuity of HCU pressure switch (102EG).
(a) Make sure that the resistance is between 6.5 and 7.5 kohms between pins 2 and 5.
(b) Make sure that the resistance is more than 100 kohms between pins 2 and 3.
(c) If you find a fault, replace HCU PRESS SWITCH ENG 1A [102EG1] or HCU PRESS SWITCH ENG 2A [102EG2] AMM 78-31-21-000-801 and AMM 78-31-21-400-801.
(d) Do the test given in Para. 3.
(8) If you find no fault or if the fault continues, replace
5. Close-up(1) Get access to HCU, EEC and pylon junction box.
(a) Remove the access panel from the pylon to get access to the HCU:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
413AL
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
423AL
(b) Open the fan cowl-doors AMM 71-13-00-010-802.
(2) At HCU pressure switch (102EG), 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 HCU-T/R, ENG1 [4310EG1] or HCU-T/R, ENG2 [4310EG2] AMM 78-31-01-000-801 and AMM 78-31-01-400-801.
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 (102EG_A) and HCU pressure switch (102EG):
1 Repair as necessary.
2 Do the test given in Para. 3.
(4) If the check is OK or if the fault continues, use a PLIERS - JAWED, SOFT to disconnect connector (102EG-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 the pylon harness:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
AWM 783611
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
AWM 783612
(b) Reconnect connector (102EG-A).
(c) Do the test given in Para. 3.
(5) If you find no damage or if that fault continues, disconnect connectors (102EG-A) and P1 from the EEC (4000KS) AWM 715135.
(a) Do a continuity check (less than 5 ohms) between the pins of connectors P1 and (102EG-A) as follows:
- Pin M and pin 2
- Pin L and pin 5
- Pin j and pin 3.
- Disconnect connector (P402) at pylon junction box.
- Pin M and pin 14
- Pin L and pin 13
- Pin j and pin 28.
(e) If you find a fault:
1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
2 Do the test given in Para. 3.
(f) If there is continuity:
1 Replace the pylon harness:
a FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
AWM 783611
b FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
AWM 783612
2 Reconnect all connectors.
3 Do the test given in Para. 3.
(6) If there is continuity between connectors P1 and (102EG-A) or if fault continues, disconnect connector (102EG-A) and do a visual inspection of the HCU pressure switch (102EG) for bent pins, contamination or corrosion, or other signs of damage.
(a) If you find damage, replace HCU PRESS SWITCH ENG 1A [102EG1] or HCU PRESS SWITCH ENG 2A [102EG2] AMM 78-31-21-000-801 and AMM 78-31-21-400-801.
(b) Do the test given in Para. 3.
(7) If you find no damage or if the fault continues, disconnect connector (102EG-A) and do a check for continuity of HCU pressure switch (102EG).
(a) Make sure that the resistance is between 6.5 and 7.5 kohms between pins 2 and 5.
(b) Make sure that the resistance is more than 100 kohms between pins 2 and 3.
(c) If you find a fault, replace HCU PRESS SWITCH ENG 1A [102EG1] or HCU PRESS SWITCH ENG 2A [102EG2] AMM 78-31-21-000-801 and AMM 78-31-21-400-801.
(d) Do the test given in Para. 3.
(8) If you find no fault or if the fault continues, replace
Subtask 78-31-00-860-053-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.
(b) Close the pylon access panel:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
413AL
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
423AL
(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.
(b) Close the pylon access panel:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
413AL
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
423AL