What was found
DURING CLIMB, PILOT ATTEMPTED TO ENGAGE YAW DAMP & REPORTED THAT IT DID NOT ENGAGE. ABNORMAL FORCE WAS REQUIRED TO DEFLECT RUDDER PEDALS HOWEVER, AS IF YAW DAMP WAS ENGAGED. PUSHING AUTOPILOT DISCONNECT HAD NO EFFECT & AUTOPILOT WOULD NOT ENGAGE. IT WAS DECIDED TO RETURN TO VNY FOR A PRECAUTIONARY LANDING SINCE THE WINDS WERE CALM & THEY WERE UNABLE TO RESOLVE THE PROBLEM. THEY DECLARED AN EMERGENCY & ADVISED ATC. APPROACH & LANDING WERE MADE WITHOUT INCIDENT. RUDDER PEDALS BECAME FREE ON THE TAXI IN TO THE RAMP.