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[CA11] Autopilot laziness and COG issues
07-29-19, 11:59 PM (This post was last modified: 08-01-19 02:07 PM by Chuck - Raymarine - Moderator.)
Post: #1
[CA11] Autopilot laziness and COG issues
I have had recent autopilot difficulties that I have been unable to diagnose. They are as follows (System configuration included below):

1. The autopilot drifts lazily off course when INITIALLY instructed to go to the cursor or go to a waypoint. Generally, after a period of time, it corrects the course. However, in some circumstances, the failure to follow the designated bearing to waypoint can be problematic. Although my autopilot is set with a relatively low default course sensitivity of 2, setting it to a much higher setting before initiating the GOTO does not alter the behaviour.

2. At rest, the displayed orientation of the vessel and course over ground do not align with the vessel and deviate tremendously from the magnetic bearing. This did not used to be the case. There are no software or configuration changes that I can think of that would have caused this. In contrast, when the boat is in motion, whether sailing or under power, the course over ground (COG) is accurately displayed. Although generally not a significant issue, this makes it more difficult to understand radar data while docked (and possibly on anchor).

What I have tested to date:
1. I have checked the resistance on the fluxgate compass leads and found that they match your posted specifications.
2. I have checked the resistances on the rudder position transducer. These are more or less appropriate, although there appears to be minor deviation from mean resistance at mid helm. The resistances, in kilo-ohms, are as follows:
hard- mid hard-over
over
red blue: 2.2 2.7 3.0
green blue 2.3 2.8 3.2
red green 4.9
3. Functional testing of COG underway. When turning the vessel very slowly in a circle, both clockwise and counterclockwise , the displayed COG on the e95 chartplotter changes slowly and smoothly, generally in two degree increments, although sometimes in 3 or 4 degree increments.

Although perhaps not perfect, the rudder transducer data does not appear bad enough to implicate it as a cause of the problem.

I do not see any magnetic materials in close proximity to the fluxgate compass. The radar data cable does pass within 1 foot of the fluxgate. However, the observed problems typically happen when the radar is in standby mode. The standard raymarine ferrite on the fluxgate compass leads located near the course computer is not large enough to permit two runs of the cable through the ferrite. As a result, only one cable run length is present inside the ferrite.

All system software is, to the best of my knowledge, up to date.

The XB8000 is a vesper watchmate ais receiver and transponder connected to the raymarine seatalk ng backbone with a nmea 2000 cable and the raymarine adaptor cable. The device is set to block gps data from the dedicated AIS gps from being placed on the seatalk network. The e95 is configured to use the internal gps.

Your help is much appreciated.

e95 E70021 0320239
v19.03-00036

SeaTalk-STNG-Converter
Product ID
E22158
Product Serial Number
1103501
Software Info
Application Version
2.03

SPx30
Software Info
Application Version
3.05

Raymarine ST70 Pilot Head
Product ID
E12196
Product Serial Number
1000355
Software Info
Application Version
3.04
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08-02-19, 07:25 AM
Post: #2
RE: [CA11] Autopilot laziness and COG issues
Welcome to the Raymarine Forum Marc,

The problem reported is not indicative of a fault with the rudder transducer. When heading errors such as you have reported occur, then the problem is typically indicative of one of the following:

- the fluxgate compass is being subjected to a magnetic field which was not present when the autopilot's compass was calibrated and aligned ... you have indicated that you have inspected the area within 3' of the compass for items which have been constructed of ferrous or magnetic materials. Cables carrying high currents or coiled cable can also produce magnetic fields.

- a fluxgate compass which is binding ... it has been noted that you have performed the resistance test for the compass. The FAQ addressing how to test the fluxgate compass additionally calls for checking the Heading (not COG) data item as the vessel is slowly turned through 360 degrees to monitor for pauses in the reported heading.

- the autopilot course computer is failing ... the course computer should be sent to Raymarine’s Product Repair Center to be bench checked / serviced.

The items listed above should be attended to in the order listed above. The most common cause for the reported symptom is a failing fluxgate compass.
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