Autohelm ST 4000+ - crazy steering

[FWB]

Sounds as if the rudder sensor has not been fitted correctly. Loosen the base bolts and with the rudder central rotate the base and lock it in position when the display reads in the middle. If the display still reads incorrectly then the sensor is faulty.

 

[dom]

Your problem won't be exactly that but the symptoms suggest either slack in the drive train or incorrect input from the rudder sensor unit. Firstly check the ram and sensor unit are moving correctly when the helm moves, then suspect the sensor.

+1 ...I traced a similar problem back to a wiggly rudder reference unit.

One more thing - OP does not mention whether unit was set "Steer to Wind Angle", "Steer to WPT", or "Steer to Bearing". If one accidentally chooses the former in a light wind the boat would indeed go on a drunken walk!

 

[dunedin]

+1 ...I traced a similar problem back to a wiggly rudder reference unit.

One more thing - OP does not mention whether unit was set "Steer to Wind Angle", "Steer to WPT", or "Steer to Bearing". If one accidentally chooses the former in a light wind the boat would indeed go on a drunken walk!

Thanks. Was set on steer to bearing.
Rudder reference was showing as centred with previous head/control unit fitted, and compass angle was reasonable - both these aspects gone kybosh when swapped this control unit (though steering was drunken before and after change)

 

[Simondjuk]

Have you selected the correct base settings, carried out the alongside calibration, swung the compass and carried out the sea-trial calibration since fitting the replacement control head?

 

[jwilson]

On a boat just under ten years old am on my third ST4000 control head. Went wrong once at about 3 years old with exactly these symptoms, had to buy (ouch) new replacement which also turned out to be faulty, then a warranty replacement on this for present one which so far is still OK, touch wood.