Message Name:

HYDRAULIC PRESSURE SWITCH INDICATION FAILURE

A failure of the Hydraulic System 1, Hydraulic System 2, Hydraulic System 3 pressure switch-indication shows on the HYDRAULIC synoptic page (HSP) of the Engine Indication and Crew Alerting System (EICAS).

• Data Acquisition Unit (DAU) 1 (A17)
• Data Acquisition Unit (DAU) 2 (A18)
• Data Acquisition Unit (DAU) 3 (A30)
• Data Acquisition Unit (DAU) 4 (A31)
• Engine-Driven Hydraulic Pump (EDP) 1A Pressure-Switch (S34)
• Engine-Driven Hydraulic Pump (EDP) 2A Pressure-Switch (S37)
• AC Motor Pump (ACMP) 1B Pressure-Switch (S36)
• AC Motor Pump (ACMP) 2B Pressure-Switch (S38)
• AC Motor Pump (ACMP) 3A Pressure-Switch (S39)
• AC Motor Pump (ACMP) 3B Pressure-Switch (S40)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Display the HYDRAULIC synoptic page (HSP) on the EICAS.
2. Release the pressure from the related hydraulic-system. Check if the hydraulic pump flow-lines between the systems EDP and/or ACMPs and the PSI indication are green.

   1. If the flow-lines are not green, do close out.
   2. If the flow-lines are green, continue with the next step.

3. Pressurize the affected hydraulic-system 1, hydraulic-system 2 or hydraulic-system 3. Check if the hydraulic pump flow-lines between the systems EDP and/or ACMPs and the PSI indication are green.

   1. If the flow-lines are green, do close out.
   2. If the flow-lines are not green, release the pressure from the affected hydraulic-system and continue with next step.

4. Check which of the following switches show HIGH or LOW indication:

   1. If it is ACMP 1B (B PUMP) pressure-switch (HIGH or LOW) indication, go to step 7.
   2. If it is EDP 2A (A PUMP) pressure-switch (HIGH or LOW) indication, go to step 9.
   3. If it is ACMP 2B (B PUMP) pressure-switch (HIGH or LOW) indication, go to step 11.
   4. If it is ACMP 3A (A PUMP) pressure-switch (HIGH or LOW) indication, go to step 13.
   5. If it is ACMP 3B (B PUMP) pressure-switch (HIGH or LOW) indication, go to step 15.
   6. If it is EDP 1A (A PUMP) pressure-switch (HIGH or LOW) indication, continue with next step.

5. Remove the DAU 2 to get access to connector A18BP1 and disconnect the connector S34P1 from the EDP 1A hydraulic pressure-switch. Perform a voltage check as follows:

   From	To	Expected Result	Result
   S34P1-B	Ground	11±1 VDC

   1. If there is 11±1 VDC, perform troubleshooting of EDP 1A HYDRAULIC PRESSURE SWITCHES FAULT CONDITION SENSED and do close out.
   2. If there is no 11±1 VDC, continue with next step.

6. Perform a continuity check for an open circuit or a short circuit to ground between EDP 1A connector (S34P1) and DAU 2 connector (A18BP1) as follows:

   From	To	Result
   S34P1-B	A18BP1-E4
   S34P1-A	Ground

   1. If there is a short circuit to ground or an open circuit, repair or replace the defective wiring as required. Connect the disconnected connectors and do close out.
   2. If there is no short circuit to ground or an open circuit, connect the disconnected connectors and perform the troubleshooting for observed fault DAU 2A (2B) FAIL.

7. Remove the DAU 2 to get access to connector A18BP1 and disconnect the connector S36P1 from the ACMP 1B hydraulic pressure-switch. Perform a voltage check as follows:

   From	To	Expected Result	Result
   S36P1-B	Ground	11±1 VDC

   1. If there is 11±1 VDC, perform troubleshooting of ACMP 1A HYDRAULIC PRESSURE SWITCHES FAULT CONDITION SENSED and do close out.
   2. If there is no 11±1 VDC, continue with next step.

8. Perform a continuity check for an open circuit or a short circuit to ground between ACMP 1B connector (S36P1) and DAU 2 connector (A18BP1) as follows:

   From	To	Result
   S36P1-B	A18BP1-H11
   S36P1-A	Ground

   1. If there is a short circuit to ground or an open circuit, repair or replace defective wiring as required. Connect the disconnected connector and do close out.
   2. If there is no short circuit to ground or an open circuit, connect the disconnected connector and perform the troubleshooting for observed fault DAU 2A (2B) FAIL.

9. Remove the DAU 3 to get access to connector A30BP1 and disconnect the connector S37P1 from the EDP 2A hydraulic pressure-switch. Perform a voltage check as follows:

   From	To	Expected Result	Result
   S37P1-B	Ground	11±1 VDC

   1. If there is 11±1 VDC, perform troubleshooting of EDP 2A HYDRAULIC PRESSURE SWITCHES FAULT CONDITION SENSED and do close out.
   2. If there is no 11±1 VDC, continue with next step.

10. Perform a continuity check for an open circuit or a short circuit to ground between EDP 2A connector (S37P1) and DAU 3 connector (A30BP1) as follows:

    From	To	Result
    S37P1-B	A30BP1-E4
    S37P1-A	Ground

    1. If there is a short circuit to ground or an open circuit, repair or replace defective wiring as required. Connect the disconnected connector and do close out.
    2. If there is no short circuit to ground or an open circuit, connect the disconnected connector. Perform the troubleshooting for observed fault DAU 3A (3B) FAIL and do close out.

11. Remove the DAU 3 to get access to connector A30BP1 and disconnect the connector S38P1 from the ACMP 2B hydraulic pressure-switch. Perform a voltage check as follows:

    From	To	Expected Result	Result
    S38P1-B	Ground	11±1 VDC

    1. If there is 11±1 VDC, perform troubleshooting of ACMP 2B HYDRAULIC PRESSURE SWITCHES FAULT CONDITION SENSED and do close out.
    2. If there is no 11±1 VDC, continue with next step.

12. Perform a continuity check for an open circuit or a short circuit to ground between ACMP 2B connector (S38P1) and DAU 3 connector (A30BP1) as follows:

    From	To	Result
    S38P1-B	A30BP1-H11
    S38P1-A	Ground

    1. If there is a short circuit to ground or an open circuit, repair or replace the defective wiring. Connect the disconnected connector and do close out.
    2. If there is no short circuit to ground or an open circuit, connect the disconnected connector. Perform the troubleshooting for observed fault DAU 3A (3B) FAIL.

13. Remove the DAU 4 to get access to connector A31BP1 and disconnect the connector S39P1 from the ACMP 3A hydraulic pressure-switch. Perform a voltage check as follows:

    From	To	Expected Result	Result
    S39P1-B	Ground	11±1VDC

    1. If there is 11±1 VDC, perform troubleshooting of ACMP 3A HYDRAULIC PRESSURE SWITCHES FAULT CONDITION SENSED and do close out.
    2. If there is no 11±1 VDC, continue with next step.

14. Perform a continuity check for an open circuit or a short circuit to ground between ACMP 3A connector (S39P1) and DAU 4 connector (A31BP1) as follows:

    From	To	Result
    S39P1-B	A31BP1-E4
    S39P1-A	Ground

    1. If there is a short circuit to ground or an open circuit, repair or replace the defective wiring. Connect the disconnected connector and do close out.
    2. If there is no short circuit to ground or an open circuit, connect the disconnected connector. Perform the troubleshooting for observed fault DAU 4A (4B) FAIL.

15. Remove the DAU 4 to get access to connector A31BP1 and disconnect the connector S40P1 from the ACMP 3A hydraulic pressure-switch. Perform a voltage check as follows:

    From	To	Expected Result	Result
    S40P1-B	Ground	11±1 VDC

    1. If there is 11±1 VDC, perform troubleshooting of ACMP 3B HYDRAULIC PRESSURE SWITCHES FAULT CONDITION SENSED and do close out.
    2. If there is no 11±1 VDC, continue with next step.

16. Perform a continuity check for an open circuit or a short circuit to ground between between ACMP 3B connector (S40P1) and DAU 4 connector (A31BP1) as follows:

    From	To	Result
    S40P1-B	A31BP1-H11
    S40P1-A	Ground

    1. If there is a short circuit to ground or an open circuit, repair or replace the defective wiring. Connect the disconnected connector and do close out.
    2. If there is no short circuit to ground or an open circuit, connect the disconnected connectors. Perform the troubleshooting for observed fault DAU 4A (4B) FAIL.

17. Do close out.