Hi all,
I have a 2014 C51 with a NMEA 2000 problem - there is no data from any instruments showing on any indicators and no autopilot available. I have checked the NMEA 2000 network and there is no 12V power at any points I can tap into. I have tried to find where the fuse is but I cannot after a few hours of searching.
Does anyone know where the NMEA 2000 network is powered from and/or where the fuse is located?
Thanks, Graham
possibly from the switch for the navigation and instruments.
In the Bavaria 51 Cruiser it is very likely on the separate relaypanel (ERP 423889) from the connection with "navigation". This panel is hidden somewhere around your navigation corner, on our 41 Cruiser behind the couch. Does your switchpanel activate the relay (on the switchpanel the pushbutton activates the controllight and it holds) and also overhere you can find the fuse..on the relaypanel...
There are two vertical rows of relays and fuses (left and right) and a horizontal row of 8 relays and fuses. Complete right one of the horizontal row is for navigation and holds a 20A fuse
Quote from: Happysailor on November 30 2025, 17:29In the Bavaria 51 Cruiser it is very likely on the separate relaypanel (ERP 423889) from the connection with "navigation". This panel is hidden somewhere around your navigation corner, on our 41 Cruiser behind the couch. Does your switchpanel activate the relay (on the switchpanel the pushbutton activates the controllight and it holds) and also overhere you can find the fuse..on the relaypanel...
There are two vertical rows of relays and fuses (left and right) and a horizontal row of 8 relays and fuses. Complete right one of the horizontal row is for navigation and holds a 20A fuse
Thanks for the reply. I've checked all of these (I know them well by now!) All relays are working and all fuses including the 20A for navigation one are good. The navigation switch and therefore relay turns on all the instruments, just no NMEA 2000 data appearing (i.e. the fields where say wind speed would be are blank, but the indicator is working). The only data I'm getting is on the chartplotter - GPS position and speed (definitely helpful!). Also, NMEA 2000 fuses are normally a 3A / 5A / 7.5A so it can't be directly from the navigation fuse.
There must be a secondary power feed off a/this fuse or a secondary NMEA 2000 board somewhere - but where on a C51?
Thanks for the help so far!
Graham
Hi Graham,
This happened to me once and was caused by a short in the connection cable for the windtransducer and the t-piece to the NMEA2000 backbone. These are connected in the fwd head on our boat, in the space with the grey water tank. Found it by disconnecting all input sensors, and after the disconnection of the windsensor all came up again. Replaced the cable from the deckconnection to the backbone and problem solved. It was exactly the same, only getting GPS input...
Perhaps worth a check with your wind and depth/ speed transducers?
Quote from: Happysailor on November 30 2025, 22:13Perhaps worth a check with your wind and depth/ speed transducers?
Thanks for the tip, I will check this weekend when I'm back at the boat. I have also bought a cable tracer :-)
All instruments were working fine, until I pushed the Autopilot Engage button, then everything went silent, so I think it's a fuse somewhere. I put my meter on the NMEA 2000 cable and no 12v on the power pins....
Graham
Update - I have found the issue and resolved the problem! Thanks to everyone for the helpful clues.
Details - I had to trace the entire NMEA 2000 network. Power is injected into the network at the stern starboard side in the cavity at the end of the berth. It is a yellow Garmin cable and connects into three 'T' junctions. A terminator is there and this is one end of the network.
All of the Garmin indicators run off the NMEA 2000 power rail. All navigation fuses were intact and 12v was being supplied.
I traced everything forward checking every T connector and drops. Eventually, following the cable run behind the radio panel, behind the galley cupboards the network had two, leads - a dropper that went to the Airmar Smart Sensor for depth and speed, the second went off the T to extend the network.
I disconnected the cable that was extending the network and every sensor bar Wind Speed and Wind Direction came up.
So I traced the suspect cable to a GND 10 unit under the mast, in the main cabin, and disconnected that end. With nothing connected to that cable, just plugging the cable in caused the network to fault - indicators still powered up, but no readings from sensors. Also there was no 120 ohm terminator on that part of the link!
So a bad cable - but why was the fault so hard to find? Well no terminator installed definitely threw me askew, looking for a break in the cable somewhere, as the CAN bus should have 60 ohms across the data lines.
It also turns out that cable had developed a curious fault. Continuity on every lead was fine. Resistance between the leads was high at 2Mohms (but it should be a lot higher than that of course!).
Putting the voltmeter on some of the pairs measured 0.177V DC - what's going on here I wondered - probably corrosion via salt water. Powering up that cable with 12 volts is when it got interesting, basically a low resistance short across the 12v appeared. So when the cable was plugged in too much current was drawn, taking down the sensors/instruments, but not the indicators (!) - but - not enough to blow the fuse.
So I managed to use this cable to pull through a new cable and also put a terminator on a T to designate the end of the network. All is well and functioning correctly.
What a mission to trace and debug!
I have photos of locations of the NMEA Network if anyone is interested I'll post.
Hi Graham, glad you found it and thanks for the extensive update!
Sounds like a similar issue what happened to me, bad cable...