The black cylinder is the compass. When you turn the steer knob, the compass should turn. Turning the compass will not turn the steer knob.
Now for the bushing. In the upper left corner of your photo
the gold colored cylinder is a motor
. When the autopilot
wants to make a course correction, it activates the motor
and that turns the steer shaft and thus the compass. The rubber bushing that couples the motor to the steer shaft is located inside
the steer shaft next to where the big oring connects on the steer shaft. This bushing has to slip when you turn the steer knob, but not slip when the motor turns. Thus, they wear out.
To test it, leave the case off, reconnect the cables
and turn the AP on. Now rotate the control head
and the motor should kick in and rotate the compass. Try moving the head
in both directions as it may only slip in one direction.
Yes, this is a very different AP, unlike any other that Autohelm