Autopilot/GPS Interface Issues

[nhschneider]

About a year ago, I installed a Standard Horizon CPV350 Chart Plotter and interfaced it to my Cetrek Pro Pilot 700. Worked great. I could enter a way point and tell the autopilot to navigate to that point. But then something happened and now when I select the navigate option on the autopilot, the wheel turns hard to the left and stays there. The technical support from Standard Horizon is certain that the problem is in the autopilot and Cetrek is out of business. I did install a spare control head for the autopilot but the problem remained. Standard Horizon suggested removing the C-Map cartridge and reinitializing the CPV350, which I did but again to no avail. Both components work normally in all other functions. The wiring is relatively new and the connections clean and tight.

Any ideas? Thanks.

[Pblais]

First thing to do is to check the fluxgate compass. It is the easiest thing to do and you can do that and not screw anything up. What you do is in mount it and if there is enough slack move it so you can sit in the slip and turn the compass in set increments first clockwise and then reverse. The reading from the helm should follow smoothly.

This may seem all too simple and obvious but it's what my good friend that has been working autopilots since they were invented did for me when we had a problem. It really is unimportant that it used to work. You need to start with the items that may actually be fixed. This will validate the auto pilot and then you can move on to the GPS interface.

Personally, I never auto pilot to a way point as a cross current can get you screwed up pretty bad. I would start by asserting that the autopilot can navigate a course without the GPS to divide the problem into one half that works from the other half. I also would hesitate on ripping anything apart since it is easy to avoid the real solution and make the problem worse or at least more complicated. If you can validate both halves then the link between must be the problem.

[Pblais]

I would disconnect the GPS and validate the auto pilot. If you can unmount the fluxgate and in the slip have someone rotate it in 30 degree increments clockwise then counterclockwise this will validate the fluxgate signal. You read the heading display and make sure the readings are smooth and following the rotations. Repeat the process a few times. This can and has been a problem on a lot of boats with all autopilots.

I get this from the guy that helped me. He has been doing auto pilots since they were invented. You can tell alot by how it displays the heading. The fluxgate works in 90 degree segments and so the transitions between them in both directions will tell you a lot. A screwed up fluxgate will really trash the performance almost totally. This really is an easy test and it means you can't screw anything up doing it and you don't have to leave the slip.

I would then validate the autopilot on the water using only a set course (no GPS input) and make sure it can operate without the GPS. If you can pass all this then you can go on to the next step. I would really hesitate from undoing too much at one time. You can make a mess and make it hard to tell what used to work from what is not not properly connected.

[Sailndive345]

I'm not familiar with your brand of autopilot, assuming it is a below-deck type;
you may also take a look at the rudder position indicator.... It may have slipped off, misleading the pilot. If the rudder position is displayed at the control unit, this could be another very simple check.

You didn't place a boombox over by your fluxgate compass, did you?.. (just kiddin' of course)

Good luck!

Sailndive345