Two 711C autopilots - one failed rudder test

[MV Mobius]

We have installed two 711C autopilots for redundancy with our Kobelt hydraulic steering. One went through the set up process just fine and it is working. The other one continually fails the rudder test giving the message: "RUDDER TEST FAILED. CHECK DRIVE CIRCUIT." This message appears about 5 seconds after the test begins by moving the rudder to starboard a bit.

Nowhere in the manual does it explain what this means. I've searched on the term "drive circuit" and it only appears once in the manual. Before describing the failure message, it says:
"Note 1: When one of the following messages appears, the rudder test could not be completed successfully. Retry the test after resolving the problem.

"This is especially puzzling because the first unit is working just fine.

If anyone can give us a suggestion as to how to resolve the problem, I would really appreciate it.

Christine

 

[Johnny Electron]

It means the pilot output power to command the rudder to move but either the rudder didn't move or the feedback couldn't sense the movement. By the sound of it, the rudder reference sensor isn't working. Do you see pilot rudder response for each and every degree both directions when turning the wheel by hand?