NMEA 2000 not working unless power cycled

[bmoney2334]

He guys I have a tz3 12 on The boat and it’s hooked to the NMEA 200 back bone. Utilizing the Simrad Precision 9 compass for heading. And the Simrad Nac3 autopilot for nav function. When starting the tz3 up I’ll have to power cycle the NMEA 2000 backbone for the tz3 to see the other devices in the backbone. Has anyone seen this before. Won’t matter if I power the backbone then the tz3 or the other way around. I have to cycle the backbone power while the tz3 is powered up.

 

[Quitsa]

I would suggest you check two things. One is the voltage on the NMEA 2000 backbone. Where is your power tap? The other is whether you have the NMEA architecture correct in terms of drops and termination resistors. My guess would be low voltage, which I know can cause this issue from personal experience with my SCX-20, especially if the drop to the satellite compass is long. In my case, the SCX-20 is mounted on the tower sunshade and the drop is over 20 feet. I solved the issue by putting an isolated power tap closer to it.

 

[Sparky Wire]

I would make sure that the NMEA 2000 power breaker is ON before powering up your NavNet as well.

 

[Lim Jahey]

I would suggest you check two things. One is the voltage on the NMEA 2000 backbone. Where is your power tap? The other is whether you have the NMEA architecture correct in terms of drops and termination resistors. My guess would be low voltage, which I know can cause this issue from personal experience with my SCX-20, especially if the drop to the satellite compass is long. In my case, the SCX-20 is mounted on the tower sunshade and the drop is over 20 feet. I solved the issue by putting an isolated power tap closer to it.

NMEA 2000 drops should never exceed 6 meters.

 

[Quitsa]

NMEA 2000 drops should never exceed 6 meters.

That is the standard but here was no option in my case because of the length of the cable run up inside the tower leg.

 

[Johnny Electron]

The bus is not proper so you are likely to have intermittent problems. NMEA rules are there with reason. They make in-line terminations and other ways around allowing long runs to have proper termination. NMEA 2000 is easy, great and complex at the same time. It is rarely easy as they envisioned.

 

[bmoney2334]

NMEA back bone is configured as so.

Terminator on both ends. 5ts between the terminators. One for Simrad Nac3 - Ap Computer one for the Simrad Ap44 control head. One for power 12v supply one for the tz3 and one for the precision 9 compass. All drops are less than 6 meters.

 

[Johnny Electron]

Sorry I was referring to Quitsa's drop that was over 6 meters. I have seen some rule bends slide by but others/most end up causing intermittent problems.

 

[Quitsa]

Sorry I was referring to Quitsa's drop that was over 6 meters. I have seen some rule bends slide by but others/most end up causing intermittent problems.

We did not have any choice given the length of the tower pipe the cable had to run up to get to the SCX-20. But since there was 12V supply available up there fed from relatively heavy gauge wire, a second power tap brought the voltage high enough at the far end to stop the intermittent drops that caused the SCX-20 to restart. I know it is not within the NMEA 2000 standards but it works...

 

[FishTech]

We did not have any choice given the length of the tower pipe the cable had to run up to get to the SCX-20. But since there was 12V supply available up there fed from relatively heavy gauge wire, a second power tap brought the voltage high enough at the far end to stop the intermittent drops that caused the SCX-20 to restart. I know it is not within the NMEA 2000 standards but it works...

There is a proper method within the standards designed for these exact situations. The SCX20 would become the end of the backbone.
Remove the terminator from the end of the backbone closest to the SCX20.
Run a cable from the backbone port where the terminator was plugged in to the SCX20 area.
Install an in-line terminator within six meters of the SCX20.
Connect a cable between the in-line terminator and the SCX20.
They have factory made cables as short as .25 meters now and the in-line terminator is not much bigger than the cable ends.