Autopilot Question

[ixtlan22]

We are getting ready to go cruising.

We have an older model Raymarine Autohelm 6000.

On the shakedown cruise, we discovered that the autopilot is not working correctly as, when we engage the unit, the boat tends to go starboard in a circle and will continue to do so regardless of any attempts at resetting or adjustment. It's important to note that the unit has been on the boat for several years and will engage and dis-engage when activated... it's just that when it does engage it only goes right....in a circle. I do not know if it's always been like this as this is our first test of this system.

Looking up in Nigel's book "Boatowner's Mechanical and Electrical Manual," it states that this problem is probably due to interference from the alternator.

We are puzzled because the control head, fluxgate compass, computer, and linear drive are all located well away from the alternator and each have their own circuit. Anyone have any ideas about what's causing this or methods of resolution?

BTW we have a spare fluxgate compass and computer onboard but have not wanted to try them until we get more ideas...especially about the alternator and if it's actually the culprit.

Ray

[Eleven]

I have the manuals for the AutoHelm 4000 on my boat which does similar. If the play in the helm is greater than 20 deg the auto cant cope. Mine has sisty deg play and it doesn't cope.
Damn nuisance when trying to navigate, trim, make coffee, etc. Need two in the cockpit at the moment. Good luck.

[JusDreaming]

Our's did that and I ended up calling Raymarine tech guys and they talked me through a fix for it!! Unfortunately I have "CRS" and don't remember what they had me do

[Pblais]

You need to start with the basics. You need rudder feedback and fluxgate compass data. Does the compass change as you move the boat. Is it accurate at least to each of the 90 degrees? Does the rudder feedback display properly. If either of these are bad then you'll get that result. The next idea would be the course computer (the expensive part). You can check the rudder feedback with a multimeter. The rudder feedback is like the volume control on a stereo. It sends out a reference voltage and gets back a reading. There is a calibration for center and the computer does the rest. You can measure the return voltage where it connects to the computer.

To test the compass unmount it from it's location and slowly rotate it and read the display on the control head. The compass works in 4 quadrants of the compass so testing the transition between them is what you need to validate. If the compass passes mounted then it should be fine and not require testing unmounted. It is possible something steel is now too close where it didn't used to be close. It happens a lot and folks are sure nothing changed. Someone put something away where it didn't used to be and thinks nothing of it.

If you can validate the reading on the control head then you know these two are not the problem. Pray for a bad rudder feedback - they are the cheapest. The compass is only a tad more. The control head would be next at about triple the compass.

I've been down this road twice on two different boats. You need to eliminate what is not a problem then zero in on the rest. With simple tools and thinking it through it is possible to troubleshoot this.

[ixtlan22]

Thanks Paul,

Sounds like good directions to get started. Like I said, I do have a spare fluxgate and spare computer so I'm sure I'll get something to work. Like all diagnostics it sounds like it's just a process of elimination.

Haven't noticed anything new around the compass or computer but I'll look a little closer.

Ray

[ChuckSK]

We had a similar problem when we took delivery of our boat. The previous owners were never able to get the autopilot to work.

The problem was that the wires to the drive unit were reversed.

Chuck

[Dick Pluta]

First try to use it without the engine running. That will answer the alternator question in short order. If that's OK I agree with the reversed wire scenario.

Dick Pluta
AEGEA

[sailorboy1]

I had that problem onceand it was becaquse the clutch wasn't fully engaged.

[Chief Engineer]

TRy resetting the unit.

[nautical62]

This seems to be a common problem. I'm having the same issue in setting mine up for the first time. The compass reading is fairly accurate at all points. The rudder gain is about 13, but when I turn on the learning mode, it goes into increasingly tight circles to port. Very frustrating.

[Chief Engineer]

I have had to recalibrate mine at the beginning of each season.

[Pblais]

The compass reading is fairly accurate at all points. The rudder gain is about 13, but when I turn on the learning mode, it goes into increasingly tight circles to port.

Having no rudder feedback signal at the computer will causes this. When the computer can't find a rudder signal it increases the rudder applied until can't apply any more. The rudder sensor is required for any operation to work. It does not really know where the rudder is unless gets signal. No signal forces it hard over and it ignores the compass data. Not being calibrated won't cause this as the rudder feedback will work but it won't have a perfect idea of where the center position is when uncalibrated. It will be able to guess so long as there is a signal. It already knows the nominal voltage range the rudder feedback can send. Voltage drop and other minor issues will come out through calibration. Calibration will store the voltage reading for the center position as well as mark the range of the rudder adjustment.

Similarly the compass will transmit a signal but it won't have the on board deviation computed until you do the circles calibration. It will basically work with no calibration just not as good as it will after. The compass calibration builds a deviation card inside the computer for every degree of heading and saves it. This should make the fluxgate readings pretty good.

The manual settings are more for the dynamics of the hull and engine and in calm water should not effect the use. At higher speeds and rough weather the settings do make the boat steer stable when adjusted assuming the power is there to control the rudder. Undersized auto pilots can't be adjusted to have more power that they have.

[nautical62]

So why doesn't it get the rudder signal and how is that corrected? I did the circles thing and that's when I got the reading of 13 I think it was. It was within what the manual said was acceptable.

[scotte]

nautical62, does your display head have a rudder angle indicator? If so, see if it is showing reasonable rudder angles as you move the wheel lock to lock.

Don't worry about the gain setting at this point - start by determining if the A/P is getting all the data it needs, as that is a prerequisite to worrying about calibration.

[ChuckSK]

The Autohelm 6000 does not have rudder feedback.