AP off course, and Heading sensor location on C30

[SJI Sailor]

On our most recent outing, the autopilot was about 15 degrees off course vs. GPS on many if not all headings. (I didn't think to assess whether it was the same at all headings, but my recollection is that it differed around the compass -- starboard at some times, and to port at others.)

This was new -- in the previous ~70 hours on our boat, it had closely matched GPS. I have two questions:

1. What are the things I should do to diagnose it? I assume at least: (A) check for large things near the heading sensor; (B) make sure the heading sensor is secure; (C) run the autopilot calibration wizard. Anything else?

2. As for checking the heading sensor: where is it on the C30? I looked everywhere I could think of, and found an unlabeled Garmin unit in the fuse box on the aft wall of the cave. Photo: http://www.tugnuts.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=71143&g2_serialNumber=1 Is that it?

FWIW, if that photo is the Garmin heading sensor, it is secure and has not had anything large/metal moved near it recently. Which poses the question of why it might have gone out of calibration -- or what other causes there might be, if any.

Thanks in advance for any help!

 

[CaspersCruiser]

I can't tell you if that is the heading sensor for your model autopilot, but if you follow the troubleshooting steps you outlined, the culprit should be found. When you positively identify the heading sensor, check to make sure no magnetic tools, such as a magnetic tip screwdriver, have been moved or rolled close to it. When I suddenly had a heading error, that was the cause.

 

[Brian B]

I had the Garmin CCU bracket fail. Here is my previous post: viewtopic.php?f=2&t=13695
If it's similar on your boat it is a black ball in a plastic bracket, I would call the factory to find it's location. If it became loose it needs to be re-aligned, the Gamin site will give you the procedure.

 

[Phil Nersessian]

I have had this happen a few times on my c30. A couple times just killing all power to the system for a few minutes then powering back up cured it. Other times the re-calibration wizard did the trick

 

[SassyRed]

If you haven’t found it yet, and if it is in the same place as in our 2017, the CCU is on the starboard side up near the captain’s chair. Access is through the cave by removing the side panels. I can’t post a pic here, but if you go to the garmin.com sit and look up reactor under marine autopilot, they have a picture.

 

[SJI Sailor]

Thanks everyone!

SassyRed: you are right. I saw the Garmin Reactor 40 unit there but incorrectly assumed that was AP controller only. In fact it includes the AHRS heading sensor, too (https://buy.garmin.com/en-US/US/p/599938) So that is solved and I know where it is! That suggests that it would be affected by moving my emergency bag that goes under the helm seat and has a handheld VHF, etc.

Phil: that is good to hear about your experience. I will see if it recurs with power on next time, and then recalibrate. The Seattle weather might delay that a while ... but I'd love to boat if we get snow as forecast next week!

Brian: good note. Now that I know it's the Reactor unit and not the other mysterious Garmin box in the cave, I'll check the Reactor attachment. I didn't do that since I thought it wasn't that box :-/

Caspers: interesting -- when I read your note I realized one recent change I had quite forgotten: we had a canvas enclosure added to the cockpit, which includes some new stainless railings. Since those make a kind of a cage, I could certainly imagine compass effects even at some distance. BTW, I highly recommend the cockpit enclosure!

I'll update soon. Cheers, all!

 

[dbsea]

Thanks everyone!

SassyRed: you are right. I saw the Garmin Reactor 40 unit there but incorrectly assumed that was AP controller only. In fact it includes the AHRS heading sensor, too (https://buy.garmin.com/en-US/US/p/599938) So that is solved and I know where it is! That suggests that it would be affected by moving my emergency bag that goes under the helm seat and has a handheld VHF, etc.

Phil: that is good to hear about your experience. I will see if it recurs with power on next time, and then recalibrate. The Seattle weather might delay that a while ... but I'd love to boat if we get snow as forecast next week!

Brian: good note. Now that I know it's the Reactor unit and not the other mysterious Garmin box in the cave, I'll check the Reactor attachment. I didn't do that since I thought it wasn't that box :-/

Caspers: interesting -- when I read your note I realized one recent change I had quite forgotten: we had a canvas enclosure added to the cockpit, which includes some new stainless railings. Since those make a kind of a cage, I could certainly imagine compass effects even at some distance. BTW, I highly recommend the cockpit enclosure!

I'll update soon. Cheers, all!

What was the outcome here? Mine is wonky again (15-20 degrees off) and seems like it's a recurring issue...

 

[SJI Sailor]

It still occurs and I'm not 100% sure why. Might be other things on the boat (I suspect a hand bearing compass that is stashed for emergencies). But I'm accustomed now to adjusting it by hand occasionally using the dealer mode. Large changes in course heading are when it shows up again.

 

[dbsea]

It still occurs and I'm not 100% sure why. Might be other things on the boat (I suspect a hand bearing compass that is stashed for emergencies). But I'm accustomed now to adjusting it by hand occasionally using the dealer mode. Large changes in course heading are when it shows up again.

Can you share a link or guidance for how you’re adjusting it in dealer mode? Ty!

 

[Maggie Anne]

I'm not sure about the dealer mode but this is what I do.

Calibration done via your autopilot control panel by running the Sea Trial Wizard. You will need a calm day and some open water. The procedure is as follows, with the boat underway in calm conditions and plenty of maneuvering room:

Select Home
Select SETTINGS (Center Button)
Select MY VESSEL from options on right hand side of screen
Select AUTOPILOT INSTALLATION SETUP from options on right hand side of screen
Select WIZARDS from options on right hand side of screen
The wizards are then available as choices. Select SEA TRIAL WIZARD

You will then be given instructions to drive the boat to calibrate the electronic compass.

Also, here is a link to a YouTube Video that explains how the Sea Trial Wizard works: https://www.youtube.com/watch?v=JZbUvr2i2rE

 

[SJI Sailor]

Agreed on the AP calibration although it may not stick over time. Here are the steps to manually set dealer mode and adjust the heading if needed:

Select MENU
SETUP
SYSTEM
SYSTEM INFORMATION
Hold center button for 5 seconds
(Dealer Mode should appear on the screen)
Select BACK
BACK
MENU
SETUP
DEALER AUTOPILOT CONFIG

Then select fine heading adjustment and make it match the compass (or straight ahead on the chart). If it gets off again -- which may happen after big turns -- then only the last two steps are needed. Dealer mode stays on until the AP is turned off.

 

[dbsea]

Thanks, I’ll give this a shot!