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Old 12-21-2018, 03:01 PM   #1
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Rudder response failure

I have an old Simrad AP20 Auto Pilot thats starting to act up. From time to time I get an alarm with a message "Rudder response failure" and to stop the alarm I put it back on standby. Sometimes I can hit auto pilot again and it will work again. On a recent 25 hour Gulf crossing it worked flawlessly for 12 hours then the alarm went off. Tried several times to put it back into Auto Pilot and got the alarm so I stopped using Auto Pilot. # hours later wind really started picking up making it difficult to maintain course so I switched it into Auto and it ran for another 8 hours until the last hour. Any ideas what to look for. The fluid resiviour sight glasses are impossible to read so would low steering fluid cause this issue or do I have something failing thats on its last leg
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Old 12-21-2018, 03:54 PM   #2
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Greetings,
Welcome aboard y'all. Just a very WAG but could be low fluid. Might just be a good excuse to refurbish the sight glasses and top up the reservoir. At worst, if that does not rectify the problem, it will eliminate that as a possible error point.
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Old 12-21-2018, 04:46 PM   #3
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Two years ago our AP 20 did the exact same thing. We installed a new rudder indicator, no help. We re-did the power supply to the course computer and that helped a lot. But, we did bite the bullet and installed a new AP, keeping the AP 20 in place.

My and the Local IT expert's best guess is the course computer is slowly failing, and of course no spare parts available.
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Old 12-21-2018, 04:46 PM   #4
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A rudder response failure message is usually 1 of 2 things, Either the drive is going bad, perhaps the brushes or possibly low fluid I suppose but normally you'll loose steering at the helm before the pump drive fails in a low fluid situation. The second,more common reason is the rudder feedback has become erratic & is failing. If the pilot tells the pump to turn & the feedback doesn't indicate that the rudders are turning, you'll get the failure message.
Run the wheel hard over to hard over & make sure the rudder bar graph is filling up smoothly on both sides.
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Old 12-21-2018, 04:52 PM   #5
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Quote:
Originally Posted by sunchaser View Post
Two years ago our AP 20 did the exact same thing. We installed a new rudder indicator, no help. We re-did the power supply to the course computer and that helped a lot. But, we did bite the bullet and installed a new AP, keeping the AP 20 in place.

My and the Local IT expert's best guess is the course computer is slowly failing, and of course no spare parts available.
Wow that's weird, Sunchaser. I can't think of too many instances offhand where a Simrad pilot gave a rudder fail flag & it was the computer. Yours was an expensive fix!
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Old 12-21-2018, 05:06 PM   #6
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Wow that's weird, Sunchaser. I can't think of too many instances offhand where a Simrad pilot gave a rudder fail flag & it was the computer. Yours was an expensive fix!
Yes, the fix could be considered expensive. But, having a very good Furuno 711C AP in place of the AP20 provides a real advantage in interfacing with other Furuno gear with improved course keeping. Also, redundancy a plus.
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Old 12-21-2018, 05:07 PM   #7
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I suggest servicing the hydraulics, ensure the fluid levels and system pressure are where they should be when you're done, and then run through the setup process, both the pier side and underway parts when able. The AP may not need setting up, but running through the setup may reveal problems with sensors or other system components. Then again, if it's an intermittent problem, there's no guarantee it'll show up during setup.

I was having intermittent problems similar to yours before experiencing a complete system failure indicated by no power to either of my two controllers. I solved the complete failure by replacing the AP computer/junction box with a used one from eBay.
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