Message Name:

STANDBY INSTRUMENT LIGHTING UNSERVICEABLE

In the flight compartment, the standby instrument lighting does not come on and go off correctly when the Cockpit Lights (Integral) Control Panel is operated. When the Master Switch on the Cockpit Lights (Integral) Control Panel is set to ON, the standby instrument lighting does not change when you operate the Center (CTR) Control Switch.

• Cockpit Light (Integral) Control Panel (AP26)
• Secondary Power Distribution Assemblies (SPDA) 1 (A13)
• Secondary Power Distribution Assemblies (SPDA) 2 (A14)
• Integral Lighting Power Supply 3 (A178)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: The faults of the standby instrument lighting are almost the same as the observed faults of the panel integral lighting. The standby instrument lighting can have the additional fault that follows: If the DC 2 bus power is not available, the integral lighting cannot be operated with the BATT bus power.

NOTE: An isolated control-panel lighting fault should be corrected independently.

1. Perform the operational test of the Cockpit Lights (Integral) Control Panel.

   1. If the operational test is satisfactory, go to step 4.
   2. If the operational test is unsatisfactory, continue with next step.

2. Check for the fault in components.

   1. If the fault shows only in the components of the standby instrument lighting and go to step 4.
   2. If the fault shows in the components of the standby instrument lighting and also in other components of the panel integral lighting, continue with next step.

3. Perform the troubleshooting for the observed fault panel integral lighting.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

4. Check for the standby instrument lighting.

   1. If the standby instrument lighting comes on and can be adjusted, do close out.
   2. If the standby instrument lighting does not come on and cannot be adjusted, continue with next step.

5. Check for the fault in operational mode.

   1. If the fault shows any one from AUTO and ON operational modes, go to step 7.
   2. If the fault shows in both the AUTO and ON operational modes, continue with next step.

6. Disconnect the connector A178P1 from the power supply unit 3 (A178), perform a 28 VDC power check within power supply 3 (A178) as follows:

   From	To	Expected Result	Result
   A178P1-F	A178P1-D	28 VDC
   A178P1-G	A178P1-D	28 VDC

   1. If the power check is unsatisfactory, replace the power supply unit 3 (A178) and do close out.
   2. If the power check is satisfactory, continue with next step.

7. Check that there is +28 VDC at SPDA 1 (A13P3) and SPDA 2 (A14P1) as follows:

   Pin	Expected Result	Result
   A13P3-n	28 VDC
   A14P1-K	28 VDC

   1. If the voltage is not correct, perform the troubleshooting for the applicable SPDA and continue with next step.
   2. If SPDA 1 and SPDA 2 are serviceable, continue with next step.

8. Disconnect the affected connectors, AP26P1 for the Cockpit Lights (Integral) control-panel, A13P3 for SPDA 1, A14P1 for SPDA 2 and A178P1 for power supply unit 3 (A178) and perform a continuity check the connectors/terminals that follows:
   For the Cockpit Lights (Integral) control-panel (AP26P1):

   From	To	Result
   A178P1-A	AP26P1-13

   For Power Supply Unit 3 (A178):

   From	To	Result
   A178P1-D	GS410
   A178P1-H	GS411

   For SPDA 1 (A13P3):

   From	To	Result
   A178P1-G	A13P3-n

   For SPDA 2 (A14P1):

   From	To	Result
   A178P1-F	A14P1-K

   1. If there is no continuity, repair or replace defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

9. Check for the fault in operational mode.

   1. If the fault shows any one from AUTO and ON operational modes, go to step 11.
   2. If the fault shows in both the AUTO and ON operational modes, continue with next step.

10. Replace the Cockpit Lights (Integral) Control Panel.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

11. Disconnect the affected connectors, AP26P1 for the Cockpit Lights (Integral) control-panel, A94P1 for EMS CDU 1, A91P1 for EMS CDU 2 and A178P1 for power supply unit 3 (A178) and perfrom a continuity check between the connectors/terminals that follows:
    For the Cockpit Lights (Integral) control-panel (AP26P1):

    From	To	Result
    AP26P1-10	GM148-B
    AP26P1-6	GM148-A
    AP26P1-16	GM148-C

    For Power Supply Unit 3 (A178):

    From	To	Result
    AP26P1-13	A178P1-A

    For EMS CDU 1 (A94P1):

    From	To	Result
    AP26P1-5	A94P1-61

    For EMS CDU 2 (A91P1):

    From	To	Result
    AP26P2-4	A91P1-61

    1. If there is no continuity, repair or replace defective wiring as required and do close out.
    2. If there is continuity, continue with next step.

12. Check for the fault in operational mode.

    1. If the fault shows only in the AUTO mode, go to step 14.
    2. If the fault continues to show only in the ON operational mode, continue with next step.

13. Disconnect the affected connectors, AP26P1 for the Cockpit Lights (Integral) control-panel and perform a continuity check between the connectors/terminals as follows:

    From	To	Result
    AP26P1-6	GM148-A
    AP26P1-16	GM148-C

    1. If there is continuity, do close out.
    2. If there is no continuity, repair or replace defective wiring as required and do close out.

14. Perform the troubleshooting for the observed fault panel integral lighting.
15. Do close out.