What was found
AUTOPILOT B WILL NOT STAY ENGAGED - TRIES TO TURN TO THE LEFT. GROUNDED - YES. CONFIRMED FAULT, DFCS BITE TEST FAILS CH-B AIL ACT PRESS LCL INV MSG 22-11149. SWAPPED FCC, STILL FAILS ON THE CH-B SIDE. RE-INSTALLED FCC INTO THE ORIGINAL POSITIONS. REMOVED & REPLACED CH-B A/P AILERON ACTUATOR REF B737-800 AMM 22-11-25. ACCOMPLISHED A/P AILERON ACTUATOR ADJUSTMENT REF AMM 22-11-25-820-801 & A/P AILERON ACTUATOR TEST REF AMM 22-11-25-801, OPS CK NML. ALSO, REMOVED & REPLACED HYDRAULIC PRESSURE SWITCH REF AMM 22-11-40, AS PRECAUTIONARY. ACCOMPLISHED DFCS LAND VERIFY (GP 49) TEST REF AMM 22-11-00 & HGS SYSTEM TEST REF SMM 34-36-00, OPS CK NML.