What was found
DURING EMERGENCY LIGHT TEST, PTP SHOWS FAULT EPSU EXT LOAD EMER. RESET POWER TO ASSOCIATED EPSU. NO FIX. COMPLETED BITE OF EPSU UNIT IAW TSM 33-51-00-810-822-A. BITE SHOWED EXTERIOR LIGHTS FAULT. WIRING CHECKED IAW TSM 33-51-00-810-822-A, FOUND RED LED EXTERIOR LIGHTS FAULT ACTIVE ON EPSU 12WL. SWAPPING EPSU 12WL & 11WL, RESULTS IN THE FAULT STAYING IN PLACE. RETURNED EPSU TO ORIGINAL LOCATIONS. PERFORMED WIRING CHECKS FOR GROUNDS ON EPSU & ALL RANG OUT NORMAL. TSM33-51-00-810-822-A SAYS TO CHECK THE WIRING OF THE SLIDE LIGHTS CONNECTOR AND THE BETWEEN APPLICABLE EPSU & RELATED EMERGENCY LIGHTS & REPAIR WIRING. REF ASM 33-51-02 SCH 01 PAGE 120C, DEU-B 300RH1 APPEARS UNRELATED TO EPSU 12WL BUT IS INSTEAD DEU-B 300RH4. REMOVED CEILING PANEL ABOVE ROW 22 TO FIND DEU-B BUT COULD NOT LOCATE. EXTERNAL LOAD FAULT SUGGESTS EITHER EXTERNAL RT OVERWING LIGHT OR RT OVERWING EMERGENCY EXIT SLIDE. SUGGEST WIRING CHECKS OF RH OVERWING LIGHTS AND/OR RH OVERWING SLIDE. ON INSPECTION OF RT AFT OVERWING EMER LIGHT ASSY, FOUND BULB CORRODED, SEPERATED FROM METAL & SEZED IN LIGHT FIXTURE. R & R RT AFT OVERWING EMERGENCY LIGHT FIXTURE. OPS CHKD GOOD. CIDS TEST OK. IAW AMM 33-51-15.