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Autopilot issue I think

Discussion in 'Electronics' started by CSkipR, Jun 1, 2014.

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  1. CSkipR, Jun 1, 2014
    #1
    CSkipR

    CSkipR Member

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    On our way to the Abacos (Green Turtle Club) the autopilot had trouble holding a course. If I engaged it on Nav to waypoint it would not hold a course. If I switched it to a heading (auto) it would hold a better course but still not good like normal. It had worked fine from north FL down to Ft Pierce but the crossing is where the problem started.
    I checked power steering fluid and pressure and fluid was fine pressure a little low at 10psi so pumped it up to 25psi.
    What would you check next?
  2. K1W1, Jun 1, 2014
    #2
    K1W1

    K1W1 Senior Member

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    Hi,

    How does the autopilot get its feedback as to where the rudder actually is?

    There is often some sort of arm and resistor coil involved, loose parts and or corrosion are common problems.
  3. CSkipR, Jun 1, 2014
    #3
    CSkipR

    CSkipR Member

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    Not sure I can answer where it receives the info on rudder position. Their is an arm connected to the rudders that I suppose sends the signal. Don't see any corrosion and everything looks connected.
  4. K1W1, Jun 1, 2014
    #4
    K1W1

    K1W1 Senior Member

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    Hi,

    Grab it and see if it wobbles around.

    Take it off the Rudder, disconnect the leads on whatever it is attached to and put your meter on the terminals to measure Ohms. Move the arm back and forth gently and see if the resistance moves smoothly. Any sudden ups or downs or open circuit will point to an issue with that component.

    If that all looks/feels good check the cable and where it connects to the head end unit. If this is via some junction box check all connections and carry on till you are satisfied all connections are good and secure.

    Where does the AP gets it's heading reference from?

    Is it possible the compass has developed an error or the pickup for the AP has fallen off/come loose there?

    What does it actually do or not do when you say it doesn't work properly?
  5. bobhorn, Jun 1, 2014
    #5
    bobhorn

    bobhorn Member

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    On our Sitex AP there is a setting that displays rudder position. If your AP can do that then slowly turn the wheel and see if the display is smooth and continuous.

    Bob
  6. dennismc, Jun 1, 2014
    #6
    dennismc

    dennismc Senior Member

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    A manual should give you some clues in the troubleshoot section, a failure of rudder feedback should cause an alarm and cause the pilot to be inoperative would be unusual for the pilot to develop a fault that is not operator error,although it has happened, go to the manual and step thro the dockside test procedure and see if all parameters are on spec.
  7. thatcher, Jun 1, 2014
    #7
    thatcher

    thatcher Member

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    recalibrate, do a dockside reset then go out and do your circles. maybe the unit lost power and went to default.
  8. Capt Ralph, Jun 2, 2014
    #8
    Capt Ralph

    Capt Ralph Senior Member

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    What has changed since it last worked. Anybody go down and get supplies around the heading sensor? Anybody put supplys away around the heading sensor? Turn an inverter on? Drop a cigar lighter or flashlight into the bilge or around the heading sensor?
    What model AP was that again?
  9. CSkipR, Jun 4, 2014
    #9
    CSkipR

    CSkipR Member

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    AP works off the heading sensor. Nothing new in area where heading sensor is located.
    Rudder display and rudder seem to be in proper working order. No corrosion or loose parts that I see.
  10. NYCAP123, Jun 4, 2014
    #10
    NYCAP123

    NYCAP123 Senior Member

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    This may be too simple, but....
    Not knowing your experience or the speed of your vessel let me mention that on auto the boat will drift off course due to current, wind, etc., it'll just keep pointing to the compass point And if you're off the course line when you put it on Nav it will try to get you back on the course line resulting in a series of "S" turns as it over-shoots it.
    Also depending on the boat, an auto pilot can't keep up with heavy seas because they react not anticipate. I once followed a 43' Ocean in about 12' following seas. I'd be looking at her stern as she went up the backs of the waves and then I'd be looking at her bowrail when she hit the bottom of the fronts. The mate was hanging on the transom chumming. I finely got on the radio and told him to get off auto before he broaches.

    How were the seas?
  11. Pascal, Jun 4, 2014
    #11
    Pascal

    Pascal Senior Member

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    When you say it didn't hold course, what where the exact symptoms? Did it let the boat drift off course in one direction until the error got so big you had to correct manually, if so by how much? Did it try to correct by steering back and forth? By how much course deviation?

    What where the conditions? Does the rudder indicator work normally and show the correct angle?

    Sometimes I see has much as 10 degrees deviations from a set heading. And yes, with following seas I usually hand steer as the AP simply can't keep up
  12. Capt Ralph, Jun 4, 2014
    #12
    Capt Ralph

    Capt Ralph Senior Member

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    We have a constant running Robertson/Simrad pump. Hate the idea the motor is always running but it came with the boat and works great.
    However, as fast as that poor lil motor can switch hydraulic pressures, it's still no match in a following sea. Compounded by Bertrams High Speed (f&^^ng small) rudders.
    We also use a Simrad AP25 and when setting in Nav mode, it deliberately induces an error, finds cross track, corrects and holds a pretty good line despite those (D^&*M) small rudders. S turns are reduced by sea-state, rudder response and error gain controls.
    Usually we have to drive the old fashioned way, wheel and throttle in a following sea.
    Rode the back of a deep swell all the way in Ponce one day. Could see the bottom over our transom. Came time for that left turn south near the end of the rocks, That's when I got nervous. Breakers on both sides. Any A P would not have a chance.
  13. Capt J, Jun 4, 2014
    #13
    Capt J

    Capt J Senior Member

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    After what you checked in your last post. Go into the menu and see what the "response" is set to, you can dial it up or down with the knob and it will react quicker if you dial it up. Also, when you hit auto does it say "hi" or "high" or "lo" or "low" on the screen? By hitting auto twice in a row (you might have to hold it down for a few seconds, the second time you push it" you can change it from the low setting to the high setting and it will react quicker. It sounds like it's one of these issues. If the response is too low, in some sea states or a different load on the boat (fuel etc) it won't react quick enough or sometimes it can react too quickly.
  14. Capt Ralph, Jun 5, 2014
    #14
    Capt Ralph

    Capt Ralph Senior Member

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    Skip
    On your way back, remember there is a dredge working now in the Ponce inlet.
    ,rc
  15. Maxwell, Jun 5, 2014
    #15
    Maxwell

    Maxwell Senior Member

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    Does the steering seem "spongy" (for lack of better term)at all when you turn the wheel? An older 52 Tiara that I ran a few weeks back was a little low on fluid. This made the helm feel a little spongy and made the AP not be able to hold course. You could hear the AP pump motor working behind the helm, however there wasn't enough pressure in that line to allow it to control the rudders. We ended up having to add fluid and bleed the air in the system.

    max