What was found
MDIS 974 33-50 7298 18FEB21 MUC OPEN U AFTER AIRCRAFT POWER OFF FOUND EMERGENCY LIGHT IN COCKPIT LEFT SIDE ABOVE DOOR AND LEFT EXTERIOR LIGHT ILLUMINATED. WITH AC POWER ON LIGHTS GO OFF . CHECKED AND MOVED EMERG. LIGHT SWITCH IN COCKPIT SEVERAL TIMES TO OFF . NO HELP. WITH AIRCRAFT POWER ON LIGHTS ARE OFF. CHECKED ALL TEST SWITCHES AND ON ARM OF SWITCH FOR FUNCTION , FOUND OK, PERFORMED ALSO SEVERAL POWER SWITCHINGS, APU AND EXTERNAL POWER. FAULT SEARCH ACC WDM33-51-11 PG 926AND WDM 33-51-12 PG 930 PERFORMED. FOUND BATTERY PACK AT M731 POWER SUPPLY NOT CORRECT INSTALLED , SCREWS NOT LOCKED. AFTER BATTERY PACK CORRECT INSTALLATION ACC AMM: 33-51-07-2 . FUNCTION CHECK NORMAL