What was found
WXR NOT PAINTING CORRECTLY. IN AUTO MODE AT FL 350 TILT IN CAL 2M SHOWED NEARLY 1/2 RED 1/2 YELLOW FROM 55NM OUT TO 200NM. MANUAL MODE 0 TILT SHOWED 1/2 GREEN 1/2 YELLOW WITH NO ACTUAL WEATHER NEAR OUR ALTITUDE. IN AUTO GAIN VAR 1 CLICK UP SHOWED 80% RED 20% YELLOW SAME RANGE. ALSO SHOW RED SPECKLES IN SPOTS SELECTING MAP MPDE SHOWED ALMOST SAME DISPLAYS IF IT MAY BE MAPPING ALL THE TIME. GROUNDED - YES. REMOVED AND REPLACED WXR DRIVE UNIT AND ANTENNA REF B737-900 AMM 34-43-00, OPENED/RESET 1EA C/B P6-1, OPS CKD NML REF AMM 34-43-00 ALL GND TESTS PASSED.