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[TG11] Autopilot looses course after about 5 minutes
03-05-20, 08:52 PM (This post was last modified: 03-06-20 11:23 AM by Chuck - Raymarine - Moderator.)
Post: #1
[TG11] Autopilot looses course after about 5 minutes
Hi forum,

The boat is a new to me 50' Schooner (monohull) with a "SmartPilot S3G-A5T" course computer and a "Smart Pilot S7001" display head. The display head had a burnt out screen and non-working buttons so I replaced it with a second hand ST70 autopilot display (that came off a catamaran). Steering is hydraulic and the autopilot drive is a Type 3 hydraulic pump M81124.

When in "auto" mode, the autopilot steers the boat but slowly/gradually seems to loose course until "off course" message is displayed and alarm starts beeping. If I press +1 or -1 the autopilot steers the new course until it runs off course again. It might hold course for 5 minutes or less, sometimes 10' or more.

I tried to run the commissioning process via the ST70 but after the "Initial Setup" the device exits the process and returns to Standby. It does not let me continue with the "Dockside" and "Sea Trial" calibration process. The "ST70 Autopilot Controller SmartPilot X Commissioning Instructions" (Document reference: 81287-1 Date: March 2008) state that the calibration process (if you wish to repeat it) can be accessed through the Advanced Options menu/ Setup wizard. However I find no such option anywhere.

So questions are:
1. Can the calibration process be accessed using the ST70? If so, how? IS there a way to reset all parameters and start anew?
2. Is it reasonable to believe that running the calibration might resolve the problem?
3. Does the "vessel type" and "drive type" information reside on the course computer or the display/control head? Because if on the display then I would have the incorrect settings from the catamaran the display came off of, correct?

Many thanks for anyone that can shed some light or point me in the right direction!
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03-09-20, 01:57 AM
Post: #2
RE: [TG11] Autopilot looses course after about 5 minutes
Hello Bambooboat,

The ST70 is fine to use with an S3G, but you won't see the same calibration options as you would with a more advanced SPX pilot.

All of the calibration is stored in the Course Computer (S3G) and so replacing the display will make no difference to the way the pilot steers. You ought to be able to calibrate via the ST70 (though it's been a lot of years since I have tried) but I wouldn't expect dumping everything and starting again. I don't think this is a simple calibration error.
  • If you steer the boat in a series of slow circles whilst in Standby, what happens with the indicated pilot heading? Does it change smoothly, evenly, consistently to match the vessel's heading? Does it seem to lag behind, or drift, or count backwards at any time? If you take the grey plastic cover off the S3G and unplug the 3-core Rate Gyro cable on the left-hand side (red-yellow-black wires, white connector, power the S3G down first) and do the same circles, does the pilot heading seem to stick/freeze and then jump at any point? If you have any unusual heading behaviour, you have a problem Rate Gyro or fluxgate compass. If the problem is throughout 360 degrees or stops when you unplug the gyro, it's the gyro. If it's only in certain sectors or continues when the gyro is unplugged, it's the fluxgate.
  • If you turn the helm very slowly port-starboard lock-to-lock several times and watch the rudder position indicator, does that ever flicker, disappear, stick, jump, count backwards? If so, you have a rudder reference fault.
  • If you turn the helm far to port and then press Auto, does the drive move it positively and smoothly to centre each time you do this? Does it do the same to starboard? If you go into Auto and make lots of +10/-10 course changes, does it always do a firm, positive movement? If not, you probably have a motor or hydraulic problem.

If I had to take a guess based on limited info, I'd say either a failing pump motor or a broken winding in the fluxgate compass.


Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots, thermal cameras
Location: Sydney, Australia.

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03-09-20, 11:50 AM (This post was last modified: 03-09-20 12:28 PM by Chuck - Raymarine - Moderator.)
Post: #3
RE: [TG11] Autopilot looses course after about 5 minutes
Thank you Tom, this is great stuff. I will need to do my homework and try out the tests you mention. I will revert when I have some answers (or more questions!).
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