Message Name:

FWD WATER PUMP NOT CYCLING WHEN LINE PURGE IS SELECTED

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

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

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: Refer to cabin Supplemental Wiring Diagram (SWD) GW3810XXXX (W/D Water System).

1. Apply power to the aircraft and make sure water system is serviced. On the external water system service panel select the "Forward system line purge" mode.
2. At the forward (fwd) 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 fwd water pump connector, make sure a ground is present on pin B.

   1. If a ground is present, replace the fwd water pump and do close out.
   2. If a ground is not present, continue with next step.
      NOTE: In Purge Mode, relay KMW103 (FWD SYS PUMP NORMAL MODE) should not be energized and the ground passes through contacts A2 and A3 of the relay.

4. Remove relay KMW103 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 KMW103 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 KMW103 (FWD SYS PUMP NORMAL MODE) should not be energized but it is normal to find voltage present at relay coil pin X1.

6. With relay KMW103 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 KMW103 (FWD 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 KMW103 FWD SYS PUMP NORMAL MODE contact X2 and relay KMW104 contact A2 and between relay KMW104 contact A1 and the Water Service Panel Selector Switch contact 6 (Aft Line Purge).

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks are good and a ground is still found at relay KMW103 contact X2, replace the Water Service Panel Selector Switch and do close out.
      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.
      NOTE: Relay KMW104 (Water Available) is controlled by relay A5-B5 inside the MHC. On purge selection, this relay should be found energized.

8. Perform a 28 VDC voltage check at relay KMW102 contact A2 (FWD 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 KMW102.

   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 KMW102 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 KMW102 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 KMW102 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 KMW102 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 KMW102 contact X2 and ground.

    1. If there is continuity, replace relay KMW102 (FWD SYS PUMP PURGE MODE) and do close out.
    2. If there is no continuity, continue with next step.

15. Remove relay KMKW103 FWD 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 KMW103 FWD SYS PUMP NORMAL MODE should not be latched (energized).

16. Perform a wiring check between relay KMW102 contact X2 and relay KMW103 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 KMW104 (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 KMW104 (WATER AVAILABLE) should be latched (energized).

18. Perform a wiring check between relay KMW104 contact B2 and relay KMW103 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 KMW104 contact 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 KMW104 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 KMW104 contact X2 and ground.

    1. If there is continuity, replace relay KMW104 and do close out.
    2. If there is no continuity, continue with next step.

22. Perform a wiring check between relay KMW104 contact X2 and the LH cabin controller (MHC) connector 1P1 pin 10 and also between the LH cabin controller connector 1P1 pin 9 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 24.

23. Perform a wiring check between relay KMW104 contact B1 and the LH cabin controller (MHC) connector 1P1 pin 41 and also between the LH cabin controller connector 1P1 pin 19 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.

24. Replace the LH cabin controller (MHC).
25. Do close out.