Simrad AP nmea2000 network problem

[Wdeertz]

I have a Simrad autopilot with both a AP28 and AP24 headunits as depicted in the attached drawing. I purchased the boat 4 months ago and everything was working fine but it suddenly stopped working after no changes. From looking at the simnet data it says “network address = fail” and gives TX/RX network errors so I presume it’s a nmea2000 network problem. From reading the manual it says small networks like this will work without termination. None of the cables have red ends so I don’t believe any of these have built in termination. I’ve disconnected everything and reconnected to ensure I have solid connections. I’ve also tried to isolate which device may be causing issues by trying as few devices as possible (AC42 and each headunit separately, etc) but its always the same result.

Anyone have any suggestions on how to diagnose what the problem is? If the entire thing bit the dust I’d replace but not sure if it’s a single device causing me issue. Thanks

 

[catalinajack]

Seems to me that the first thing to do is to install terminal ends and see what happens. Easy to do, inexpensive. Yours does not look to be a "small" network in any case.

 

[oguidry]

Post your question on the Marine Electronics Forum on

https://www.thehulltruth.com/

Some real Simrad experts there.

 

[Wdeertz]

Seems to me that the first thing to do is to install terminal ends and see what happens. Easy to do, inexpensive. Yours does not look to be a "small" network in any case.

Yes I had already ordered 2 terminators before posting this question. I thought someone might have some insights to share while I wait for the terminators to arrive, no such luck

 

[kchace]

Very few devices incorporate termination, usually low cost devices that are anticipated to be used in a very small like 2 device network. Your network should absolutely be properly terminated. At least start there. I’m not sure about that AP setup but some devices have diagnostics that can be run from a system menu. See if you have that. If the diagnostics and the termination don’t clear it up for you, try disconnecting one device at a time.

Ken

 

[kchace]

This is a pretty good description of how a network should be set up with a few dos and donts

https://www.simrad-yachting.com/hel...nd-Build-an-NMEA-2000-Network&guideId=003-779

 

[STB]

Since it was working and then totally vs intermittently stopped, something likely changed. Check the 12v supply to the network bus. There is often a fuse. Then find two devices that will work together on the net and add devices until it doesn't, one at a time. Once you find a device that won't work swap cables and see if that helps.

The bus should be terminated, but given the history, I suspect there is more going on.

 

[twistedtree]

As I recall, the AP control head has a diagnostics page for N2K where it will report Rx and Tx errors. I would start by checking that. There should be ZERO errors. If there are ANY, then there is a problem.


If you have errors, start by disconnecting everything except the minimal AP parts to allow the head to operate, and see if there are still errors. If there are, then it's the head or it's the network wiring. If you have two heads, try each independently since it's unlikely both developed problems at the same time.


And I agree about terminating the network properly, which I think you are in the process of doing. If it works without termination, it's just because luck is with you at the moment.