What was found
AT START OF APPROACH, DISENGAGED AUTO-PILOT BUT FOUND CONTROLS AND TRIM STIFF OR JAMMED. COMMANDED AUTO-PILOT DISCONNECT AGAIN BUT NO CHANGE. TRIED ELECTRIC TRIM ALSO BUT WITHOUT CHANGE AND GOT NO TRIM MOTION. THEN SAW THAT AUTO-PILOT ENGAGE LEVER HAD NOT MOVED TO OFF POSITION AS EPECTED AT DISENGAGE. MANUALLY MOVED LEVER TO AFT/OFF POSTION AND RE-GAINED NORMAL FLIGHT CONTROLS. ENTIRE EVENT TOOK ABOUT 6 SECONDS. SUBSEQUENT SERVICE FOUND AUTO-PILOT ENGAGE LEVER JAMMED AND FRICTION PREVENTING IT FROM MOVING BETWEEN ON AND OFF POSITIONS.