Central Locking System - '85 930. Key unlocks both doors, but driver's side will not lock with key (knob depresses and releases with clunking sound). Central lock button on console illuminates but will not lock doors (it dooes unlock passenger door). To secure car, must manually lock driver's door from inside and manually lock passenger door from inside and close door. Is there a fuse / relay that controls this function? Switched solenoids inside door panels with no change.