As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
A/P B DISENGAGES SHORTLY AFTER SELECTION. TRIED 3 X'S. A/P A WORKS NORMALLY. GROUNDED - YES. REPLACED "B" AUTOPILOT AILERON ACTUATOR WITH SERVICEABLE UNIT AND C/W AUTOPILOT AILERON ACTUATOR ADJUSTMENT. ADJUSTMENT AND LEAK CHECKS OK. REF B737-900 AMM 22-11-25. 14 MIG 51A'S INSTALLED / REMOVED. ACCOMPLISHED DFCS LIBRARY TEST 60.31 PER MM 22-11-25-710-801 - ALL TESTS PASS. REMOVED C/N 16022487 AND NOTIFIED SEAMC JOE. CLEARS MEL 22-1F AND MEL 22-99B.