What was found
AT FL 390 AUTOPILOT A, DISENGAGED IN FLIGHT. NEITHER A OR B WOULD ENGAGE AFTER ABOUT ONE MINUTE. ACFT GROUNDED. DFCS FFR LEG 1 HAS MESSAGE 22-11208 LOGGED SEVEN TIMES ON CHANNEL A ONLY. IAW FIM 22-13 TASK 818, REMOVED AND REPLACED MAIN ELECTRIC STAB TRIM RELAY R64. ACCESS PANEL LEAKED CHECK OK. DFCS FAULT MESSAGE LRU TESTED GOOD. DFCS BITE LIBRARY SPEED, STAB TRIM 32> TEST PASSED. ACCOMPLISHED DFCS LIBRARY TEST IAW AMM 22-11-00-740-806, DFCS LAND VERIFY TEST (GP 49) IAW AMM 22-11-00 & HGS TEST IAW SMM 34-36-00, OPS CHECKED NORMAL.