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WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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07/06/21

Message Overview:

Message Name:

AFT WATER PUMP NOT CYCLING WHEN LINE PURGE IS SELECTED

Message Code: 381OBS001
Effectivity: 9111, 9113, 9115, 9118-9120, 9122, 9124, 9126,9129, 9134, 9137-9139, 9143 and 9144
System: Potable Water System
System Description: 38-10-00
Schematic Diagram: None
Wiring Diagram: None

Message Description:

The After Water Pump is not cycling when LINE PURGE is selected.

Possible Causes:

  • Left Hand Cabin Controller
  • Water System Pressure Switch
  • Water System Water Sensor
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. Apply power to the aircraft and make sure water system is serviced. On the external water system service panel select the "AFT system line purge" mode.
  2. At the aft water pump, verify that there is 28 VDC at pin A of the pump connector.

    1. If 28 VDC is not present, go to step 8.
    2. If 28 VDC is present, continue with next step.

  3. At the aft water pump connector, make sure a ground is present on pin B.

    1. If a ground is present, replace the aft water pump and do close out.
    2. If a ground is not present, continue with next step.
      NOTE: In Purge Mode, relay KMW107 (AFT SYS PUMP NORMAL MODE) should not be energized and the ground passes through contacts A2 and A3 of the relay.

  4. Remove relay KMW107 and verify that a ground is present at pin A3 of the receptacle.

    1. If a ground is not present, repair defective wiring as required and do close out.
    2. If a ground is present, continue with next step.

  5. With relay KMW107 still removed, install a jumper between contacts A2 and A3 of the receptacle.

    1. If the pump does not start, go to step 8 (voltage seeking).
    2. If the pump starts cycling, continue with next step.
      NOTE: In Purge Mode, relay KMW107 should not be energized but it is normal to find voltage present at relay coil pin X1.

  6. With relay KMW107 still removed, verify if there is a ground present at contact X2 of the receptacle. There should be no ground.

    1. If a ground is not present and step 5 checks were successful, replace relay KMW107 (AFT SYS PUMP NORMAL MODE) and do close out.
    2. If a ground is present, continue with next step.

  7. Perform a wiring check between relay KMW107 AFT SYS PUMP NORMAL MODE contact X2 and relay KMW105 WATER AVAILABLE contact A2 and also between relay KMW105 contact A1 and relay KMW108 contact B2.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If a ground is not found at relay KMW107-X2 and step 5 was successful, replace relay KMW107 and do close out.
      NOTE: Relay KMW105 WATER AVAILABLE is controlled by relay A14-B14 inside the MHC. On Purge selection, this relay should be energized. Relay KMW108 (Low Pressure) should not be latched in purge selection.

  8. Perform a 28 VDC voltage check at relay KMW106 contact A2 (AFT SYS PUMP PURGE MODE).
    NOTE: In Purge mode, this relay should be latched (energized).

    1. If 28 VDC is not present, go to step 10.
    2. If 28 VDC is present but not at pump connector pin A, continue with next step.

  9. Perform a wiring check between the pump and relay KMW106.

    1. If the wiring checks are not good, repair defective wiring as required and do close out.
    2. If the wiring checks are good, continue with next step.

  10. Perform a 28 VDC voltage check at relay KMW106 contact A1.

    1. If 28 VDC is present at A1 but not at A2, go to step 12.
    2. If 28 VDC is not present, verify the DC Cabin Feeders via the EMS CDU and make sure they are all IN and continue with next step.

  11. Perform a wiring check between relay KMW106 contact A1 and the circuit breaker panel.

    1. If the wiring checks are not good, repair defective wiring as required and do close out.
    2. If the wiring checks are good, continue with next step.

  12. Perform a 28 VDC voltage check at relay KMW106 contact X1.

    1. If 28 VDC is present, go to step 14.
    2. If 28 VDC is not present, verify the DC Cabin Feeders via the EMS CDU and make sure they are all IN and continue with next step.
      NOTE: A Terminal Module (TM) might be present in the system between the relay and the Water Service Panel Selector Switch. Make sure the input and output of the TM are good and replace if necessary.

  13. Perform a wiring check between relay KMW106 contact X1 and the circuit breaker panel.

    1. If the wiring checks are not good, repair defective wiring as required and do close out.
    2. If the wiring checks are good, continue with next step.

  14. Perform a continuity check between relay KMW106 contact X2 and ground.

    1. If there is continuity, replace relay KMW106 AFT SYS PUMP PURGE MODE and do close out.
    2. If there is no continuity, continue with next step.

  15. Remove relay KMKW 107 AFT SYS PUMP NORMAL MODE and perform a continuity check between receptacle contact B2 and ground.

    1. If a ground is not present, go to step 17.
    2. If a ground is present, continue with next step.
      NOTE: In purge mode, relay KMW107 AFT SYS PUMP NORMAL MODE should not be latched (energized).

  16. Perform a wiring check between relay KMW106 contact X2 and relay KMW107 contact B3.

    1. If the wiring checks are not good, repair defective wiring as required and do close out.
    2. If the wiring checks are good, replay relay KMW103 and continue with next step.

  17. Remove relay KMW105 (WATER AVAILABLE) and perform a continuity check between receptacle contact B1 and ground.

    1. If there is no continuity, go to step 23.
    2. If there is continuity, continue with next step.
      NOTE: In purge mode, relay KMW105 (WATER AVAILABLE) should be latched (energized).

  18. Perform a wiring check between relay KMW105 contact B2 and relay KMW107 contact B2.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  19. Perform a 28 VDC voltage check at relay KMW105 WATER AVAILABLE pin X1.

    1. If 28 VDC voltage is present, go to step 21.
    2. If 28 VDC is not present, verify the DC Cabin Feeders via the EMS CDU and make sure they are all IN and continue with next step.
      NOTE: A Terminal Module (TM) might be present in the system between the relay and the Water Service Panel Selector Switch. Make sure the input and output of the TM are good and replace if necessary.

  20. Perform a wiring check between relay KMW105 contact X1 and the circuit breaker panel.

    1. If the wiring checks are not good, repair defective wiring as required and do close out.
    2. If the wiring checks are good, continue with next step.

  21. Perform a continuity check between relay KMW105 WATER AVAILABLE pin X2 and ground.

    1. If there is continuity, replace relay KMW105 and do close out.
    2. If there is no continuity, continue with next step.

  22. Perform a wiring check between relay KMW105 WATER AVAILABLE pin X2 and the LH cabin controller (MHC) connector 1P1 pin 27 and also between the LH cabin controller connector 1P1 pin 28 and ground.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, go to step 29.

  23. Perform a wiring check between relay KMW105 (WATER AVAILABLE) pin B1 and relay JK9661-4 (Aft Line Purge) pin A2 located on aft relay panel.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  24. Perform a continuity to ground check at relay JK9661-4 (Aft Line Purge) pin A1.

    1. If there is no continuity, repair defective wiring as required and do close out.
    2. If there is continuity, continue with next step.
      NOTE: In the AFT line purge mode selection, relay JK9661-4 (Aft Line Purge) should be latched (energized).

  25. Perform a 28 VDC voltage check at relay JK9661-4 (Aft Line Purge) pin X1.

    1. If voltage is present, go to step 27.
    2. If 28 VDC is not present, verify the DC Cabin Feeders via the EMS CDU and make sure they are all IN and continue with next step.

  26. Perform a wiring check between relay JK9661-4 contact X1 and the circuit breaker panel.

    1. If the wiring checks are not good, repair defective wiring as required and do close out.
    2. If the wiring checks are good, continue with next step.

  27. Perform a continuity check between relay JK9661-4 (Aft Line Purge) pin X2 and Ground.

    1. If there is continuity, replace relay JK9661-4 and do close out.
    2. If there is no continuity, continue with next step.

  28. Perform a wiring check between relay JK9661-4 (Aft Line Purge) pin X2 and the LH cabin controller (MHC) connector 1P1 pin 44 and also between the LH cabin controller connector 1P1 pin 24 and ground.

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  29. Replace the LH cabin controller (MHC).
  30. Do close out.

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