What was found
CAPTAIN'S RADAR INACCURATELY DISPLAYS WEATHER AHEAD IN AUTO MODE AND SUPPRESSES KNOWN WEATHER AHEAD IN MANUAL MODE. INFLIGHT TEST PERFORMED IAW MULTISCAN RADAR CHAP 6 PG 10 AND DID NOT RECEIVE ANY FLASHING TILT CODES! GROUNDED - YES. FOUND WEATHER RT UNIT HOLD DOWN SCREWS 2-3 FULL TURNS LOOSE. RESECURED RT UNIT, REF B737-800 AMM 34-43-41. OPS CHECK OK, REF B737-800 AMM 34-43-00-710-802-001. (NOTE: WAVEGUIDE NOT FIRMLY SECURED AGAINST RT UNIT CAUSES ANOMALIES IN FLIGHT.) NO FAULTS NOTED.