What was found
THE MULTI-SCAN RADAR UNIT IN THE AUTO MODE IS NOT SHOWING ANY RETURNS OVER AN AREA OF OBVIOUS CONGESTIVE ACTIVITY INCLUDING LIGHTNING AND OTHER PILOT REPORTS. GC MODE WHEN ACTIVATED SHOWS NORMAL TEST RESULT. IN THE MANUAL MODE ABLE TO IDENTIFY CELLS. GAIN MODE SET AT 12 O'CLOCK POSITION WHICH IS NORMAL. ACFT GROUNDED. PERFORMED WEATHER RADAR TEST IAW AMM 34-43-00, OPS CHECKED NORMAL. AUTO MODE OPS NORMAL. NO HISTORY 30 DAYS. ALL GROUND FUNCTIONAL TESTS PASS.