Offset / compass issues with vx2 system

[stevemitchell]

I just bought a new boat and it came with a full suite of Furuno equipment that needs some assistance to get it working correctly again. According to the previous owner, it was working perfectly for many years, but got screwed up in the last year or so. I don't know what happened to cause this, so I'm working to get it corrected without any of that information.

I've reverse engineered how everything is connected, and included a diagram below.

The issue has to do with the various pieces related to orientation. While sitting at the dock, this is what I see:

Chart plotter GD1920C - 55 degrees
Autopilot control heads - 69 degrees
Radar image - offset 10-20 degrees
Normal binnacle compass (verified by two different locations) 85 degrees

Obviously this is not right. On the chart plotter, I can see the course line for the boat is clearly at least 30 degrees off to port - our marina is very large and the line veers off quickly.

When using the radar, the overlay on a chart is also off quite a bit.

The pieces I have in the system:

GD1920C/NT chartplotter
GP-320B GPS
RSB-0070 Radar
FAP-7002 autopilot control unit
Rudder response unit
PG-500 heading sensor
FAP-7011C autopilot control head in salon
FAP-7021 autopilot control head at flybridge
Standard Horizon VHF sending AIS to GD1920C/NT

Configuration:

GD1920C/NT ports:
Port 1 - GP-320B GPS
Port 2 - Standard Horizon VHF (38400 bps)
Port 4 - From FAP-7002 auto pilot control head

I validated these are seeing data by starting the GC1920C in install quick test mode and seeing the NMEA output, and matching the sentences. Data is being seen and looks good on all three ports.

I've looked for settings for an offset or other things on the chart plotter, but haven't found any set. I also verified that the chart plotter is using magnetic, not true.

That is only the chart plotter, which is off by about 30 degrees (55 vs 85)

The autopilot is also off - it shows 65-69 when it it should be 85. I assume that gets its reference from the PG-500, and I have validated that it is working OK. I did the diagnostic tests and it came back OK. When it boots up, it shows normal status (just the Status light lit).

I feel like I might have two problems here, but I am not sure. I really need to get this tuned correctly to be safe when using the system. I've read a ton of other posts where people had one or the other problem, and usually it was related to compass calibration, but I don't know if that is the problem here.

Your help is appreciated!

 

[Johnny Electron]

Try following the steps of this post.

viewtopic.php?f=4&t=3443&p=12604&hilit=heading+align#p12604

 

[Flatline]

stevemitchell,
thank you for your inquiry. It is quite possible that you may have more that one issue which complicates the trouble shooting process.
First, understand that Heading and COG (course over ground) are two different / distinct pieces of data. From your "GD1920-55 degrees" statement; I don't know which you are referencing. Obviously "sitting at the dock" the COG of the GP1920 will be completely inaccurate (you need to be underway at sufficient speed so as to properly generate a course for the GPS to track).
If you have ensured that all devices are displaying Magnetic rather than True, verify that while underway the GOG should not be vastly different from your binnacle compass. Certainly not 30 degrees, but its typical to see a slight difference between the COG and the vessels compass (some more on other points of the compass cardinals than others)
Secondly, once this is resolved lets verify the radar alignment; align the radar and the radar only (do not use radar/chart overlay function). ensure that any target dead off the bow of the vessel correctly appears at the 12 o'clock position of the radar screen. Instructions can be found for this process in the installation manual [url]https://www.furunousa.com/en/support/1934C--NT. [/url]Section 3.1 explains the setup & radar alignment process.
To access the installation menu hold the MENU key in while powering the unit ON. Continue to hold the Menu key until the splash screen picture of the boat appear, then you can release the menu key.
Finally, it also certainly appears that your PG500 heading sensor may need to be recalibrated. Sometimes a significant relocation of the vessel to somewhere with a different degree of magnetic deviation (Florida to Maine of instance), or even unintentionally placing/relocating a metal object (a tool box for example) somewhere near the PG500 can cause a significant change to the heading output of the compass. Realize that the PG500 supplies this heading information to the GD1920 & certainly explains why the chart/radar overlay is off as well. Instructions for calibration & setup of the PG500 can be found in the operators menu; https://www.furunousa.com/en/support/PG500R

 

[stevemitchell]

Thanks for both of your posts. I already tried the steps in the first post referenced, but I will go back and double check them.

I did try to calibrate the PG-500 this weekend FOUR TIMES but it never completed. I followed the installation manual exactly, and even tried circles the opposite direction. I started out by clearing or resetting the PG-500 since I do not know what state is in.

Here is more clarification on the headings:

Binnacle compass shows 90
Autopilot heads show 75 Magnetic
Chart plotter shows COG 30.6 magnetic
Top of radar screen on chart plotter shows 91 magnetic

Definitely seems like the radar adjustment/offset is something I can fix when using a chart overlay. But it does appear that the PG-500 (which I assume is sending the 75 magnetic data) is wrong.

Any tips for trying to calibrate the PG-500? I'm doing ~2 minute circles at 3-4 knots.

One other note - there are some older and newer components combined in this system. The chart plotter, radar, GPS and upper helm autopilot control are all similar vintage. The rudder indicator, FAP-7002 controller, and lower helm autopilot control all look newer (much newer) - the PG-500 I have no idea vintage-wise.

The chart plotter has Program No. 195002404. 03, 07* and is a C-MAP NT MAX. Not sure if there is a newer version of software and if that would fix this.

 

[stevemitchell]

No other thoughts?