What was found
WEATHER RADAR INOPERABLE IN AUTO MODE. PAINTS RED AND DOESN'T SEEM TO ADJUST TILT FUNCTION. STAYED AT 2 THE ENTIRE TIME PAINTING ALL RED ON BOTH NAV DISPLAYS. FLIGHT CONDITIONS WERE CLEAR WITH NO WEATHER CONFIRMED VISUALLY. MANUAL MODE SEEMED TO WORK NORMALLY. GROUNDED-YES. INITIAL EVALUATION, PERFORMED BASIC GVI OF R/T + FAN, CHECKS NORMAL, FULLY SEATED. PERFORMED WXR OPERATIONS TEST, IAW B737-900 AMM 34-43-00-710-802-001 AND SYSTEM TEST IAW AMM 34-43-00-730-802-001, ALL TESTS PASS. ALL MANUAL CONTROLS OPERATE NORMALLY AS REQUIRED. REMOVED AND REPLACED WXR CONT PANEL AS PRECAUTIONARY, IAW AMM 34-43-91-000/400-801. PASSES INSTALL TEST.