Autopilot CCU Location on R-31?

[Wee Venture]

Hello all. Does anyone know where the CCU (Course Computer Unit) for the Garmin autopilot is located on the newer R-31s? I saw an older post that said it was behind the top drawer next to the refrigerator but I couldn’t find it there on ours. We took delivery of the boat last August. It is technically a 2018 model. Our autopilot stopped working and after calling Garmin I had to install updated firmware and redo the sea trial wizard. I am trying to get it as accurate as I can but it occurred to me that I should know where the CCU is because I believe it has a fluxgate compass that could be affected by magnetic sources and ferrous metals. I want to be careful where I run wiring and store other objects. For example, I just stored spare anchor rode under the forward section of the v-berth that includes galvanized chain.

Also, should the digital readout heading on the autopilot pad at the bridge agree with the Ritchie magnetic compass? It seems to me that since they both are supposed to align with magnetic north (or am I wrong about that?) they should agree. But they are off by about 10deg sitting at the dock and seemed to be off by about 20deg when I was underway a couple of days ago. (I also noticed the radar overlay was rotated by about the same amount from the chartplotter’s outline of the shoreline.)

We are still in our first year with a Ranger Tug but are enjoying our boat very much and have found this site very helpful! Thanks in advance to anyone who has info on this.

 

[BB marine]

This is an issue I have had for 2 years. Sometimes it is right on and other times it is off by as much as 25 degrees. I launched the boat Yesterday and has I was doing all my checks I checked the headings at the dock. I received a new pair of binoculars for Christmas that have a compass in the viewing. Yesterday I turned Auto pilot on chart plotter and the heading on both was 25 degrees off from my compass. I used my binoculars to see which was correct compass was in agreement with binoculars. I hope someone can explain what is going on. I called Garmin about this and they responded that the compass was off.

 

[ixlr8]

....... I hope someone can explain what is going on. I called Garmin about this and they responded that the compass was off.

After a Garmin tech told me that the AIS600 uses the GPS antenna to transmit the VHF signal... I don't have much faith in Garmin support.

 

[BradOwens]

On our R29 the CCU was behind the bottom drawer, not the top drawer.

We just ran the sea trial wizard again after having the autopilot and chartplotter bearings go haywire. Now everything lines up as it should except the magnetic compass, which is off by a few degrees. Using the chartplotter on "North Up" and comparing everything with what we actually see ahead of us, I can confirm that the chartplotter and autopilot readings are correct, and the radar overlay now matches the shoreline precisely.

 

[Red Raven]

I struggled with this (compasses not matching and GPS not matching radar) much of last season. I eventually found two issues.

First, I keep an IPad on the dash as a backup chart plotter and backup camera view screen. The IPad has magnets in it that seriously screw up the magnetic compass on the dash. To get any reasonable reading for the compass the iPad has to be well away from the dash. Other items on the dash may have a similar effect.

Second, last year we bought an electric folding bike and were storing it in the 1/4 berth. The CCU is also in the 1/4 berth on the R27. Moving the bike in an out was the reason the CCU heading was messed up. This off season I moved the CCU up higher as far as it will go with the current cables. I have yet to test it this season with the (now two) bikes in the 1/4 berth. I may have to move the CCU to another area altogether. It is my understanding that the calibration done by the Sea Trial wizard will often be able to correct for fixed metal items near the CCU. The bigger problem is with metal or magnetic items that move after the calibration is completed which ruins the calibration. Of course our bike was being moved with each use and thus screwing up the calibration each time.

 

[Wee Venture]

OK, regarding the CCU, I did find it behind the bottom drawer, hiding behind a horizontal plywood strip at the back bottom part of the cabinet. (Thank you, Brad!) I had to feel back there with my hand and use an inspection mirror to verify that’s what it was. It’s good to know because I plan to run some wiring through that very area and now I’ll know to suspend it higher up with cable ties rather than let it rest on the bottom where it would be right on top of that unit.

Regarding the problem of the compasses/chartplotter/radar not matching, I very much appreciate the feedback. It’s nice to know it’s not just me. And that at least someone has had some success in dealing with it (again, thank you Brad and also thanks to Curt of Red Raven). I actually just got a full size iPad myself and downloaded Navionics charts to use as a backup. Having a backup system is looking like a better and better idea but I’ll be careful where I put it.

I’m going to take the boat out again and try to get it working better. It occurred to me that when I was at the dock a while back, I used the fine tuning adjustment on the autopilot to make it match the compass. It may be that this is not a good idea when the boat is stationary at the dock, because the autopilot may be less accurate than when the boat is underway. I’ll play around with it some more and let you know. Meanwhile if anyone else has a success story I’d love to hear.

John

 

[BB marine]

I'm on board the boat now, I checked for magnetic interference. My compass is agreeing with the binocular compass. The heading (plotter and auto pilot are 150 degrees, compass 175 degrees. Sitting in the marina. When cruising the radar overlay is off from chart plotter estimated at the same degree of offset. The strange part about this is sometimes the heading setting and compass agree. This agreement happens without any movement of equipment in the boat it comes in and then returns to off sets from 5 degrees to 25 degrees. When this happens I check my signal strength ( as per Garmin instructions) Signal strength is strong. I will seek out information on running a Sea trial wizard. I too agree it is good to know this is an issue other are experiencing. Any information for a resolution is appreciated. Todays project Sea trial wizard. Thanks all!

 

[knotflying]

"Also, should the digital readout heading on the autopilot pad at the bridge agree with the Ritchie magnetic compass? It seems to me that since they both are supposed to align with magnetic north (or am I wrong about that?) they should agree. But they are off by about 10deg sitting at the dock and seemed to be off by about 20deg when I was underway a couple of days ago. (I also noticed the radar overlay was rotated by about the same amount from the chartplotter’s outline of the shoreline.)"

Unless the is no current or wind the magnetic compass will not align with the GPS readout. The magnetic compass will give you a reading of where the bow is pointed. The GPS readout will give you the heading the boat is traveling. They are rarely the same. Also, if you never had your compass swung your headings on the compass can be many degrees off from actual. Now add to that "Variation" which is different depending where you are in the world and it has to do with the curve of the earth. As an example, where I am now the variation is about 10 degrees, so If I wanted to go on a heading of 090 I would have to head 080. So the upshot is, if you want to get somewhere in the electronic age follow your GPS. If you want to use a chart and sextant then swing your compass, know your variation, know your compass deviation, know the current and wind and start doing your math. 😀

 

[Red Raven]

In the settings of your GPS you can set it to to show the boat heading and not the GPS direction of travel. When comparing the headings you must do this first or you will be dealing with the difference in actual travel direction vs. boat heading as Knot pointed out.

BBmarine,
Yes, the Sea Trial wizard is what you need. I had the same problem where it was calibrated in one direction and way off in the other. The Sea trial will fix this. Note that the Sea Trial wizard is only available in the dealer mode. Each version of chart plotter has different way to turn on dealer mode and access isn’t obvious via the manual. Google dealer mode for your chartplotter and you should find it OK. Note that the Sea Trial must be done on the water underway in calm water with plenty of room.

 

[BB marine]

Thanks Mike and Curt. Between what both of you have stated and what I have read today google searching I have a better understanding of why I have experienced the offsets. Mike your explanation confirmed my understanding of what I read. My problem is most likely not a problem. I am going to do the sea trial wizard. It may be a while Lake Michigan is bit rough with a NE wind. Thanks