[DG] [DG11] ST7000 / Linear drive unit doesn't engage

[LaurensenKitty]

Hello,
Our Autohelm Linear Drive / ST7000 combo is a super steering machine. I've had some trouble with it, which I would like to discuss here and hopefully find a solution.

What happens is: I engage the autopilot on the head unit. Display reads 'auto'. I can hear the Drive running, but it's definitely not steering the rudder. Normally I would feel the Drive engaging by a short vibration -like a click- in the steering wheel. This however doesn't happen. I've had it not engage for three times now.

Every time the problem occured, was while under power (engine) shortly after a long (multiple days) continuous sail, either while dropping the sails or en route to a anchorage or marina. Under sail there's no problem at all.

Can anyone tell me which part may be a suspect, or what might be the problem?

[Derek - Raymarine - Moderator]

Hi LaurensenKitty

Thank you for your enquiry.

The issue is likely associated with the clutch operation, as soon as AUTO is selected, the clutch should engage and the steering wheel will feel 'locked', operating the course change buttons will initiate a turn.

The clutch should be 12v operation, regardless of whether the main power is 12v or 24v. If you have a voltmeter, check the clutch output voltage, if you get a minimum of 12v out of the computer, then check the cabling and the clutch voltage at the drive unit, if less than 12v, then there is a damaged cable or loose connection.

The odd thing here is that you say this only happens when under motor, not when sailing and after an extended sail, this suggests maybe an issue with the charging system onboard, which only becomes obvious when the batteries are reasonably discharged after a prolonged sail. Possibly the charging system outputs a spikey voltage when charging at a high rate and this is causing a low voltage for the clutch of the drive?

temporarily connect the clutch of the drive to a separate well charged battery and repeat the scenario and if this cures the problem, then further investigation of the charging system is needed.

Thanks
Derek