What was found
SUSPECT EMERGENCY LIGHT BATTERY IS WEAK OR DEAD. ALL EXIT LIGHTS TEST WITH MASTER SWITCH ON, BUT BACK HALF DO NOT ILLUMINATE WHEN MASTER IS OFF. CORRECTIVE ACTION: REMOVED DEFECTIVE FORWARD EMERGENCY BATTERY PACK P/N 9913/1 S/N 2457 AND INSTALLED CUSTOMER SUPPLIED OVERHAULED EMERGENCY BATTERY PACK P/N 9913-1, S/N 1742. REMOVED DEFECTIVE AFT EMERGENCY BATTERY PACK P/N 9913-1 S/N 991 AND INSTALLED CUSTOMER SUPPLIED OVERHAULED EMERGENCY BATTERY PACK P/N 9913.1 S/N 834. CHARGED EMERGENCY BATTERY PACKS FOR APPROXIMATELY 1.75 HOURS AND PERFORMED FUNCTIONAL/OPERATIONAL TEST WITH NO FAULTS OR DEFECTS NOTED, IAW CESSNA CE-560 XL MM33-50-01-2 AND TC-5XL-33-191202R1 01/19/2020.