Message Name:

EMER LIGHTS INTERMITTENTLY ILLUMINATED WHEN SELECTED OFF

The issue of the lights intermittently being illuminated while in the 'OFF' position.

The key to finding the cause of the fault is getting proper identification of which lights are coming on Interior, exterior, floor path, exit signs, reading lights. The crew reported that ALL emergency lights were coming on, when in fact only the interior lights were on.

The R MAIN BUS supplies the emergency lighting power supplies with 28 VDC. If the EMER LTS switch on the LIGHTING control panel is set to ON, the power supplies provide 6 VDC to the emergency lighting system. If the EMER LTS switch is set to ARM and the R MAIN BUS becomes unserviceable, the power supplies provide the emergency lighting system with 6 VDC from the internal batteries.

• Lighting Control Panel (PL13)
• Emergency Lighting Power Supply 1 (ELPS) (PS3)
• Emergency Lighting Power Supply 2 (ELPS) (PS4)
• Diode Module (TM215)
• Diode Module (TM304)
• Remote Data Concentrator (RDC) (A13)
• Data Concentrator Unit (DCU) (A14)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Notice To Operators (NTO): None

Flight Operation Notifications Manual (FONM): None

1. The fault was isolated by noting that two reading lights 6 & 7 were not illuminated. Interchanging EBPS FWD and AFT changed the position of the two lights 8 & 5 that were not lit.