What was found
AFTER FLAP RETRACTION ON FLIGHT 3600 FTC, NO CAT 3 LAND, AND WINDSHEAR INOP. LIGHTS STARTED FLASHING RANDOMLY AND CONTINUOUSLY, AP STILL UNABLE. AFTER SELECTION OF FLAPS 18 FOR LAND ALL LIGHT OUT, THEN STARTED AGAIN AFTER FLAP RETRACTION AND ON GROUND. MAINTENANCE REPLACED LT FLAP DUAL POSITION SENSOR, REFER 409 NR 082583 FOR DETAILS.