Raymarine ST6000 Autohelm.

[stillabitofanovice]

Hi all.
Autopilot engages but doesn't steer. here's the story so far. Advice welcome.
The control unit is fine. No error codes. Display is ok. Buttons beep when pressed. Autopilot engages when Auto button pressed.

I reckon the compass is fine. It gives a sensible reading at all times. Alarm sounds when autopilot realises it can’t get the boat on course.

The only problem is that after the autopilot is engaged, it is locked solid, and doesn’t respond to +10, -10 commands. Wheel works fine when autopilot is disengaged, so the hydraulic parts are not seized.

I unplugged and reconnected the computer unit in case it was just a connection. No change.
Any ideas?

 

[pvb]

I have a PDF of the service manual, with details of diagnostic testing, circuit diagrams, etc. If you'd like a copy, send me a PM with your email address.

It rather sounds like a circuit board fault though....

 

[lpdsn]

I had an ST6000 when I first bought the boat. I never got it working and I blamed the display. Eventually re-used the drive (type-1 electric) and replaced the rest with Raymarine Evolution.

Yours sounds quite similar. Do you have the type 1 drive? Your clutch is obviously working correctly if the steering locks up. Does the arm move the steering at all? It would be worth checking the wiring between the control unit and the drive. Should be four wires if it's the same as mine (not sure it is if hydraulic), two for the clutch, and two power wires which reverse polarity to determine the direction of movement.

Very worthwhile checking the power supply to the control computer. Voltage drop can cause issues. When I fitted the Raymarine ACU I beefed up the supply to 6mm2.

My guess is that your compass is OK. Is your rudder reference arm working fine? Worth checking it is physically connected as well as electronically.

 

[prv]

I'm a bit hazy about some of the Raymarine pilot model names, but I assume this is a system with a separate drive unit. Is it actually hydraulic as you say, or one of their electric "linear drives"?

Does the "brain" apply voltage to the clutch and drive wires when it wants to turn? EDIT: Must be powering the clutch as you say the steering locks up.

If you disconnect the drive from the brain and apply 12v directly to the clutch wires and the drive wires, does it move?

Pete

 

[stillabitofanovice]

Thanks. I have the manual, but there's no mention of this particular fault.

 

[stillabitofanovice]

Haven't done those tests yet, Pete. It looks like similar to the unit in your picture though.

 

[rotrax]

From direct experience please try the following.

1. Hit the auto button and check the wheel locks. If so the clutch is working.

2. Give a large course alteration-+10, +10, +10 degrees. The wheel should turn in the correct direction and the moror should go whirr-whirr- whirr.

3. If it does it is working .

4. If it does not, hit the wheel with the palm of your hand in the direction you expected it to turn. If the motor whirr's and the wheel moves you will find the brushes in the motor are stuck, the comm. is dirty and possibly-as mine was-there is plenty of life in the brushes but the springs that apply the pressure onto the top of the brushes so they are in firm contact with the comm. are hitting the top of the brush holder.

5. Re-shape the springs with needle nose pliers, clean the comm. and brushes and reassemble.

Ours has been fine since I did the above four seasons ago.

Good Luck.

 

[prv]

Haven't done those tests yet, Pete. It looks like similar to the unit in your picture though.

Ok, so talk of hydraulics is a complete red herring as the unit is purely electric. Testing whether the brain is trying to drive it, and whether it will run directly on 12v, will reliably isolate the problem to either the electronics or the drive.

There are no brains in the drive, it's purely an electromagnetic clutch (which seems to be working), an electric motor (which may or may not be), and some mechanical transmission bits which again may or may not be ok but you'll know about it if you can hear the motor running but the rod doesn't move.

If you disconnect the drive from the steering mechanism to work on it, take care not to run the drive right up to its end stops by applying power directly. Reportedly this can damage it; in use it relies on a combination of the physical stops built into the steering system and the pilot brain knowing where to stop.

Pete

 

[lpdsn]

Ok, so talk of hydraulics is a complete red herring as the unit is purely electric. Testing whether the brain is trying to drive it, and whether it will run directly on 12v, will reliably isolate the problem to either the electronics or the drive.

There are no brains in the drive, it's purely an electromagnetic clutch (which seems to be working), an electric motor (which may or may not be), and some mechanical transmission bits which again may or may not be ok but you'll know about it if you can hear the motor running but the rod doesn't move.

If you disconnect the drive from the steering mechanism to work on it, take care not to run the drive right up to its end stops by applying power directly. Reportedly this can damage it; in use it relies on a combination of the physical stops built into the steering system and the pilot brain knowing where to stop.

Pete

+1

I had the same concerns about running the drive to the end when testing mine. Easy to rig up a simple test with a bit of forethought though.

OP should remember to engage the clutch during the test, or the motor will whirr but the connecting rod won't move.

Clutch is +12V and 0V. Drive polarity is reversed depending on which way it is to move.

 

[stillabitofanovice]

Thanks all. I'll try the mechanical test suggested by rotrax first. Gut feeling is that it will be the motor brushes, as the problem surfaced after a few months disuse over the winter. Thanks to all for the input. When I get it sorted I'll post the outcome.

 

[prv]

I had the same concerns about running the drive to the end when testing mine. Easy to rig up a simple test with a bit of forethought though.

I just put it in the middle by hand, then only touched the wires to the power supply for a second or two each way . I was testing and repairing it on the bench, bought second-hand as "not quite working right", all that had happened was a circlip gone missing in the clutch mechanism :encouragement:

Pete