That solves the conflict they have but doesn’t keep the single one from instance 0, that said I haven’t sniffed the pgns they push when only one is on the network.
As I recall they still transmit GPS and I think a few other PGNs all the time, but with blank data. That's what messes up other devices. The M506 advertises itself as a GPS, sends the GPS PGN, and does so as a high-priority device. If you hook up an 0183 GPS, that's the data that it repeats on N2K. But otherwise it sends blank data in the GPS PGNs. Some other devices see the newly advertised high priority GPS source and actually believe it. Silly them. They switch to the M506 GPS, but because there is no valid date, devices start to complain about loss of GPS. Eventually the devices figure it out and dump the M506 switching back to whatever they were using before.
Actual behavior is very device specific because none of this behavioral stuff is specified by N2K, and lots of people do it lots of different ways. I think 100% of the N2K problems I have encountered are behavioral with respect to message exchange, and it's all because it's not specified. N2K Certification doesn't look at that at all. Nada, zero, zilch. That was the basis of my N2K Standards Committee nomination to the Wall of Shame.
Ironically, it's two M506s that trip over each other the most. But the Furuno TZ2 triggered the same behavior as well. Use a TZ2 to scan the network and display available data sources, and you will find the M506 showing up as a source for all sorts of unlikely data. If you believe it, it's really a jack of all trades and the only device you need for a complete network....
Just kidding of course.
Most of the problems go unnoticed unless you are looking closely. And even things like a momentary GPS alarm get ignored when it clears and doesn't return until the next time you get under way.
