[TG] [TG11] diagnosing issue with ST4000 wheel autopilot

[laurentdubois]

Hello,

I'm looking for help with diagnosing the following problem with my ST4000 wheel autopilot.
After working properly in auto mode for a certain period of time with no issue (about an hour or so), the autopilot will start turning hard to the starboard side and go in a circle.
Then going to standby mode, the autopilot will continue acting weird and display 4001 (is that an error code?).
I verified that nobody placed any metal near the compass when the problem occurred the first time.
This has happened 3 times since, and cannot use the autopilot reliably anymore.

Thanks

[Tom - Raymarine - Moderator]

Hello Laurent,

- After the problem occurs and you go to Standby, in what way does the pilot act weird? Just shows 4001, or other stuff, and if so, what?
- Does the unexpected turn always happen to starboard?
- How do you get it working again - power cycle?

Normally, when a pilot goes hard-over one way after working successfully for a time, it's either:
- broken winding in the fluxgate compass, making and breaking contact intermittently; when broken, you'll get a 'dead sector' of static heading. Next time the problem occurs, see if you can steer slow circles and watch the indicated pilot heading (on the pilot display or a repeater, e.g. chartplotter) and see whether it turns smoothly, consistently and evenly throughout - if not, your fluxgate is suspect.
- a dead spot on the rudder-reference, if there is one, which is intermittently causing the pilot to think that the helm is hard port, causing it to drive starboard to correct.

The '4001' display sounds like either an internal fault (non-repairable...) or marginal power-supply causing the 4000's CPU to brown out, either of which could well be triggered by the extra load caused by the helm driving rapidly hard-over, perhaps because of a rudder-reference fault.

Perhaps a video of the behaviour might help, if you can coax it to happen again at the right time. Other than that, you can either work through the above or it might be time to consider a new pilot.
Regards,
Tom

[laurentdubois]

Hello Tom,


- After the problem occurs and you go to Standby, in what way does the pilot act weird? Just shows 4001, or other stuff, and if so, what?
It continues to try adjusting course and randomly steer hard to starboard even though it's in standby mode (with no effect since the clutch is disengaged)


- Does the unexpected turn always happen to starboard?
Yes, always to starboard


- How do you get it working again - power cycle?
We turn it off for a while and then start it again.

Normally, when a pilot goes hard-over one way after working successfully for a time, it's either:
- broken winding in the fluxgate compass, making and breaking contact intermittently; when broken, you'll get a 'dead sector' of static heading. Next time the problem occurs, see if you can steer slow circles and watch the indicated pilot heading (on the pilot display or a repeater, e.g. chartplotter) and see whether it turns smoothly, consistently and evenly throughout - if not, your fluxgate is suspect.

From what I remember, I won't able to do this unless I first power cycle the autopilot to get it back a normal state.
Is the fluxgate component replaceable?


- a dead spot on the rudder-reference, if there is one, which is intermittently causing the pilot to think that the helm is hard port, causing it to drive starboard to correct.
There is no rudder reference in this setup.

Perhaps a video of the behaviour might help, if you can coax it to happen again at the right time.
Other than that, you can either work through the above or it might be time to consider a new pilot.
Regards,
Tom


Thanks Tom.

[Tom - Raymarine - Moderator]

Quote:It continues to try adjusting course and randomly steer hard to starboard even though it's in standby mode (with no effect since the clutch is disengaged)

That's not good. That's not just sensor input, that sounds terminal to me. It's it's not just the belt-wear-levelling partial rotation on power-up that some of the wheeldrive models do at startup, being triggered by low supply voltage, then I think it's broken and time for a new pilot. It sounds like it's had a fair life-span.

Regards,
Tom

[laurentdubois]

Thanks Tom for your help.

[Tom - Raymarine - Moderator]

No problem, sorry it's not better news.
Tom