What was found
UPON REACHING THE AIRCRAFT AND CONNECTING BATTERIES WE PLACED EMERGENCY LIGHTS INTO ARM POSITION, PER POWER ON CHECKLIST. NO EMERGENCY LIGHTS ILLUMINATED. PLACED SWITCH INTO ON POSITION, NO LIGHTS ILLUMINATED. CONNECTED BATTERIES AND PERFORMED THE EMERGENCY LIGHT OPERATONAL CHECK, ALL CHECKS GOOD. COULD NOT DUPLICATE DISCREPANCY. APPLIED APU POWER AND LET EMERGENCY BATTERIES CHARGE FOR 1.5 HOURS. OPERATION CHECKS GOOD AGAIN, NO DEFECTS NOTED, REFERENCE CE-680A AMM 33-50-00.