Hi,
During our 20 day Atlantic crossing earlier this year we noted that our Simrad AC42/AP28/NSS7 stopped working on a regular basis with an error message on the displays (AP28 and NSS7) saying: No Autopilot Computer. Pressing STANDBY and then AUTO again solved the problem and the autopilot did its work wonderfully for another 24 hours. During many days the error was so regular that we sat in front of the AP28 waiting for it to occur and sometimes it did, even on the minute exactly 24 hours after the previous error. Sometimes it differed five or ten minutes but still very close to 24 hours between errors. Pressing STANDBY+AUTO always fixed the problem and gave us another 24 hours of good work.
I downloaded the erorlog from the NSS7 and we could see on the timestamps that it was often exactly 24 hours between alerts.
Does anybody here recognize this annoying behaviour ?
Thanks, Johan
Johan, We have the same AC42/AP28 connected via N2K only. I don't have that exact problem, but do get an error message about every three hours, "No Compass Data" or something like that. I believe my issue is in fact the compass I'm using, (Airmar H2183). In your case, I would look carefully at the N2K connection between AC42 and the network. Sounds like the data from the AC42 is being kicked off the network for a split second and restored when you go to standby and back. These a frustrating problems. I would much prefer a total failure then one that's intermittent.
Have you updated to the latest firmware in all devices?
Nowadays the simplest way to check is to connect your MFD to the internet and let it verify automatically with Navico. My own MFD is connected permanently and sometimes I get on board and it will announce that new software is available for one or more devices.
Kees & Johan, From what I can tell Simrad/Navico have all but abandon further updates to the AP28/AC42. the last software update only extended the serial numbers for manufacturing. My Simrad AP does a terrific job in the most challenging conditions, however, I have not been able to get to the bottom of the repeat error messages every three to four hours. Most of the time it was "No Compass Data" but I also saw "No nav data" as well. My N2K network is relatively simple and no other device is showing errors or performance issues. I do have a mix of brands onboard - Garmin 7612, GMI20's, Airmar transducers and some Maretron and Actisense. Restoring from the error message is the same as Johan posted - Go to Standby and back to NAV and all is well for another three hours or so.
Johan, did you ever solve your issue since the original post back in Sept? I have a new Precision 9 compass installed but have not launched the boat and tested it yet.
The last or one-but-last update did increase the 'ping timeout' between AP and AC, so that it doesn't show 'no autopilot computer' when a ping did not get through because the bus was busy.
If you have multiple devices from different brands this gets even more important. Older firmwares from various brands are 'famous' for causing too much traffic. (Furuno, Simrad, Airmar, to name but a few...)
I'm running an AC42 + Precision 9 (NAX) + AP24 combo myself, with network loads at 35-40% and have had zero issues since the last round of updates (and replacement of RC42 by NAX).
I had previously similar issues. After updating all Simrad units to the latest software versions early last year the problem disappeared. I upgraded AC12, AP24, NSS and NSS Evo2 and the problem happened much more infrequently, it was first when OP10 was upgraded to v1.4.06 (released January 2016) the problem completely disappeared. AP24, NSS, NSS Evo2 and OP10 are all autopilot controllers so they all, if present, have to be upgraded along with AC12 for the 'ping timeout' fix to be functional.