What was found
DURING A RAIN STORM FLIGHT PERSONNEL REPORTED TO RAMP 66 MAINTENANCE DEPT THAT AC. WINGS AND TAIL STROBE LIGHTS CAME ON. MAINT MECH CHECKED BATTERY SWITCH. SWITCH WAS TURNED OFF. DURING TROUBLESHOOT AFT COMPARTMENT FLOORING WAS REMOVED BEHIND PASSENGER SEATS. WATER WAS STANDING 2 INCHES IN BELLY OF AC. BATTERY RELAY WAS STANDING IN WATER. AFTER REMOVING, WATER WAS FOUND INSIDE OF THE RELAY. RELAY HAD LARGE PITTING HOLE AND SHOWED SIGNS OF ARCING.