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kcolborne

N2k network troubleshooting

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I have a mostly Garmin instrument setup on my boat.  Cockpit displays, chart plotters, wind instruments, autopilot.  It all communicates over a N2k network.
I installed everything in the boat.  It is all proper molded end connectors, T's, and terminators.
It has been working for a few years now without an issue.

This weekend when out sailing, all my cockpit instrument displays quit working.  They were powered, but acted as if they were receiving not data.
The autopilot controller lost communication with the autopilot at the same time and quit.
No warning.  It all quit at once.

I shut everything off for a few minutes and powered the instruments back up.
2 of the 5 displays had data after power up for a few seconds.  Data appeared correct.   Then they quit again.
The other 3 displays powered on, but didn't show any data.

 

I haven't started troubleshooting yet.  I was too tired to have proper patience to start working through this.
I have never had trouble with this network before.  Wondering if anyone can offer suggestions on where to start the troubleshooting based on the failure method?

 Otherwise I will check fuses, power, terminating resistors, etc.
If I don't find anything, I will start removing devices from the network until I get it to come back up.

 

 

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The Garmin G wind nexus converter to n2k spits out some garbage that will put a pilot into stby.  It's totally random and they more or less refuse to address it. Not sure if that has anything to do with your issue.  You have to use a n2k to 0183 converter then bring data on via 0183 to deal with it.

Mertron has a tool you can download online and enter in all components on a n2k network to verify if it's all good. Each component has a C number that I think is power draw.  It may be that you are right on the edge and need to add another power drop.  Unlikely but in some cases you need to setup device instances, if you have alot of the same thing IE GMI20 displays.  I can't remember but I don't think you could configure the Garmin devices, I think I used our Simrad pilot to set them all up and address.

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I have seen the autopilot doing that too, always remove that from the circuit when looking for a problem.

Get some terminators and tee pieces.

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Ill bet you find a corroded ground 

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For anyone following I spent a bit of time troubleshooting this last night.  I am pretty sure I found the problem.

Got to the boat, powered up the devices on the network.
When my Chartplotter powered up, I went into settings and looked at the device list on the network.
All devices were visible on the network and a quick check showed all devices working.
This lasted for maybe a minute, before devices started disappearing off the network list and errors started.
The errors were communication only.  Power was not lost.
Within a couple of minutes ALL devices had lost communication and nothing was visible on the device list.

I started by checking that I had 12V on the network.
I was 99% sure I did because the Garmin display units powered up and they are powered by the network.
I checked for shorted wires in the network.  None found.
Disconnected power cable from network and measured resistance to ensure proper terminating resisters were in place.
I didn't find an issue.

So I started physically inspecting wiring.
My Network has 3 main areas where devices are installed.
In each of these areas there is a group of T connectors.
I started at the back of the boat and followed the network forward.
When I got to the area under the chart table below where the T connectors are for the chart table devices, GPS, VHF, N2K USB adapter, I found the issue.
The T connectors are mounted at the back of a small cabinet under the table.
One of the T connectors was physically damaged, badly.  One end kinked at a 45 degree angle.
I don't know how this happened.  Something must have got shoved in there really hard at some point or rough weather bounced things around, but it seems it finally failed.

When I removed the T connector it was in 2 pieces.
With this connector removed, everything else on the network worked fine.
So I will buy a new T, and make a small guard for it so it can't happen again.

Fun Fun.

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1 hour ago, kcolborne said:

One of the T connectors was physically damaged, badly.  One end kinked at a 45 degree angle.

There's nothing like that feeling of finding the root cause of the issue!

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good find and thanks for the follow-up. so many seldom do.

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