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Old 07-01-2010, 14:38   #1
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Boat: 38' Marine Trader
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Autopilot Problems

Our Simrad/Robertson AP300 has worked fine for four years. After launching this year we found its heading was way off. Rotating the RFC300 fluxgate compass by hand barely changed the heading so I assumed the problem was the compass. Simrad tech support suggested an RC25 rate compass as a replacement.

Here's where it gets interesting. I installed the RC25, turned the autopilot on and I had an accurate heading. After about five minutes, the control head consistently issues a "Control Unit Failure" alarm. Simrad support had me do a master reset of the autopilot and the control head is now stuck in "Setup Required" mode and I can no longer get a heading. Contrary to the manual and RC25 instructions, there is no way to specify the compass type in either the user or installation setup menus. I tried connecting the old RFC300 compass to see if I would be able to select the compass type but no dice. I swear I saw the compass type in the user setup menu before I switched compasses. The autopilot's rudder angle feature still works properly so this appears to be compass related. I've checked all robnet connectors and even plugged the old compass back in with the new cable.

Simrad support now says I should find a technician at a dealer to troubleshoot. Anyone have experience with these autopilots or have any ideas for a solution? The RC25 compass was expensive and I'm not sure what to do next.

- Rick
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Old 09-01-2010, 08:51   #2
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Did you store any metallic items, food cans, cooking pans or similar near the fluxgate? This is often found to be a problem, further, fluxgate compasses can normally be electrically checked with an accurate ohm meter against known manufacturers values to determine if they are 'out of spec' and require replacement.

Regarding any replacement of the fluxgate compass with a new model or even the same type will require calibration. Here is a link to the Simrad/Navico manual section Manuals
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Old 09-01-2010, 16:55   #3
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We have always been very careful to keep anything metallic away from the heading sensor. When I suspected it was the problem I even put an old speaker magnet in its vicinity to see if I could get a reaction from the compass but it did not respond. I did notice that a connector on the printed circuit board at the top of the RFC300 compass was wet with oil and the board smelled like it may have had a short. I have been unable to find any technical specs so I don't know how to test either fluxgate as you suggest.

It is possible that the autopilot's compass calibration procedure could resolve the problem (I'll try that soon). But even Navico tech support said the dockside/installation settings should clear the "Setup Required" state. I have the original AP300 manual but I haven't found any other technical documentation at Simrad's site.

- Rick
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