Need Help Simrad AP20 Autopilot

[kurtzr]

Yesterday, our simrad ap20 autopilot was acting up. Noticed that the rudder indicator on the ap20 display was bouncing around wildly from port to stb while the boat was on a steady course (auto pilot in standby mode). Figured it was a loose rudder sensor as this has happened before. Checked it today, and it is still tight on the rudder and the sensor mount. Couldn't find any loose connections on the circuit board either. At the dock today, the rudder indication seems correct when I move hard over port to starboard and back to center. Rudder test in the setup menu also indicates OK

Trying to figure out if the sensor went bad internally or if this is an indication that the main ap20 circuit board has failed. Units have performed flawlessly for 16 years.

Any help anyone can offer would be greatly appreciated.

[DeepFrz]

Could also be a corroded wire terminal. Check all your connections from the rudder sensor to the AP.

Rudder sensors are, so far as I know, adjustable resistors. They can wear and the detritus can cause them to become erratic. They may react differently at the dock than in a seaway.

The link below is for an RM rudder sensor but you may be able to find the test procedure online for yours.

Actually I may be wrong that it is just a variable resistor. Check out this thread.

http://www.cruisersforum.com/forums/...elp-50137.html