Very Exciting Autohelm

[zambant]

Hope someone can help.
My Moody 34 has a Raymarine ST4000 Autohelm Wheelpilot and 99% of the time it works fine

BUT

at random times and in all sorts of varying conditions it will suddenly turn the boat to port - about 20 degrees - and its always to port.

Can't find any evidence of faulty or broken wiring.

Anyone any ideas please?

Thanks

John

 

[RichardTaylor]

Something affecting the fluxgate compass (mobile phone etc)?

 

[ParaHandy]

Every time the 4000 powers up it turns the rudder by about that amount but I can't remember whether it's to port or starboard.

If it was an inadvertent re-powering that would not surprise me at all (with this kit).

 

[zambant]

Something affecting the fluxgate compass (mobile phone etc)?

Hi Richard,
I did have that problem and removed the offending oil filters and spanners next to the fluxgate - but it still persists

 

[krissteyn]

I had a similar problem - isolated it to keying the mike on the vhf - seemed worse on ch 16

 

[DogWatch]

Every time the 4000 powers up it turns the rudder by about that amount but I can't remember whether it's to port or starboard.

If it was an inadvertent re-powering that would not surprise me at all (with this kit).

If that is what happens, I would rather have my simrad react that way. The Simrad quietly drops into standby (I think when I allow the battery to run down), quietly going to standby means it can be a while before we notice the boat is wandering off course. I think that the RM method is probably an annoyance, but I can totally understand why they have designed it that way. I would go as far as saying, a brilliant design feature.

 

[SAMYL]

Mine had similar problems until I discovered that my mobile phone was mounted on the other side of the bulkhead from the control head. Text messages coming in affected it. Moved the phone so no further problems.
On start up the motor always resets; maybe as suggested above there was a power break or voltage drop to trigger the resetting sequence.

 

[zambant]

I had a similar problem - isolated it to keying the mike on the vhf - seemed worse on ch 16

Just been down the boat - radio has no effect, none of other onboard systems seem to be a problem but still did it after 22 mins.

 

[MASH]

I'm speculating...

It sounds as if the a/p is known to exhibit this behaviour with a power interruption. Sounds to me like a good avenue to follow. "Power interruption" could perhaps also be a voltage drop rather than an open circuit.

Two possibilities suggest themselves on this line of thought;

It could be an intermittent wiring fault - in the feed or return. I know you've checked these but there can be some strange effects with poor contacts that seem to work at normal voltages/demands (static load with a continuity /ohms tester) but break down when a bit more load (maybe from elsewhere) is applied. What else is fed from the same supply to the a/p? Have you verified the grub screws on the bus bar/connectors are all really tight? I know this sounds like egg-sucking but sometimes a bit of corrosion on a connector that is actualy tight can disappear with a wee tweak of the screw. Also fuse posts - it can take only a tiny amount of corrosion on an inline fusepost to interrupt the current required- I spent days tracing a starting fault on a Yanmar engine to the fuse contacts on the 12v feed to the starter solenoid - but only when the fridge was running...
All earth connectors - and especially the earth busbar are often ignored and many problems can be caused by poor contact there. The slightest sign of corrosion or green fuzz there is a sign.

And that is the second point. See if you can isolate this problem to other kit that is running, it just might be that when the fridge starts which involves a second or two of mighty amps the voltage drops a bit due to a poor contact and off the a/p trips. That contact could be anywhere from the battery to the distribution board I suppose- if the fridge (or whatever) made a demand on the domestic system with a systemic poor contact somewhere that dragged the voltage down - bingo.

I wonder if jury-rigging a temporary trial power supply direct from either battery for a few days might show a difference and point to the part of the system at fault? But clean the battery terminals first!

Best o' luck!

Electrickery! Who'd have it?

 

[zambant]

I'm speculating...

It sounds as if the a/p is known to exhibit this behaviour with a power interruption. Sounds to me like a good avenue to follow. "Power interruption" could perhaps also be a voltage drop rather than an open circuit.

Two possibilities suggest themselves on this line of thought;

It could be an intermittent wiring fault - in the feed or return. I know you've checked these but there can be some strange effects with poor contacts that seem to work at normal voltages/demands (static load with a continuity /ohms tester) but break down when a bit more load (maybe from elsewhere) is applied. What else is fed from the same supply to the a/p? Have you verified the grub screws on the bus bar/connectors are all really tight? I know this sounds like egg-sucking but sometimes a bit of corrosion on a connector that is actualy tight can disappear with a wee tweak of the screw. Also fuse posts - it can take only a tiny amount of corrosion on an inline fusepost to interrupt the current required- I spent days tracing a starting fault on a Yanmar engine to the fuse contacts on the 12v feed to the starter solenoid - but only when the fridge was running...
All earth connectors - and especially the earth busbar are often ignored and many problems can be caused by poor contact there. The slightest sign of corrosion or green fuzz there is a sign.


And that is the second point. See if you can isolate this problem to other kit that is running, it just might be that when the fridge starts which involves a second or two of mighty amps the voltage drops a bit due to a poor contact and off the a/p trips. That contact could be anywhere from the battery to the distribution board I suppose- if the fridge (or whatever) made a demand on the domestic system with a systemic poor contact somewhere that dragged the voltage down - bingo.

I wonder if jury-rigging a temporary trial power supply direct from either battery for a few days might show a difference and point to the part of the system at fault? But clean the battery terminals first!

Best o' luck!

Electrickery! Who'd have it?

So after a weekend of sailing and fault finding - it does not appear to be a wiring problem and I ran a seperate power and return and the unit still exhibited the veering off to port at random times.

However - when we sat in port with the unit on for 2 hours it worked fine......

 

[alahol2]

Sticky compass gimbals?

 

[cliff]

So after a weekend of sailing and fault finding - it does not appear to be a wiring problem and I ran a seperate power and return and the unit still exhibited the veering off to port at random times.

However - when we sat in port with the unit on for 2 hours it worked fine......

Try a separate battery ie the only thing connected to it being the autohelm. next thing i would do is recalibrate the FG compass then if still a problem "borrow" another FG and swap them out to see if the fault is in your compass.
Check for anything metallic near the FG compass - I had one that for no apparent reason would throw the dummy out and do all sorts of strange turns - tracked the "fault" down to SHMO putting the rubbish bag in the cockpit for disposal and if there was any metallic item in it the compass threw a fit - even aluminium "tins"