The two French women stayed on the boat until Saturday afternoon February 15 when they flew to Monterrey Mexico to meet a French friend who is living there.
I spent the week searching the web to diagnose the autopilot problem. I learned that the error message occurs when the autopilot computer attempts to alter course by sending power to the autopilot linear drive. The linear drive motor should then activate and force the linear drive piston in or out to turn the boat’s rudder. The autopilot computer monitors the Rudder Sensor which detects when the boat’s rudder moves. If the Rudder Sensor does not report rudder movement within 20 seconds of the autopilot computer sending power to the autopilot linear drive, the autopilot reports the error message “autopilot drive stopped”. The error can occur because the autopilot computer failed to send power to the linear drive, the linear drive failed to respond to the power sent to it and did not move the rudder, or the rudder sensor failed to report that the rudder moved.
I found a very useful post from someone who had the same Raymarine autopilot with the same error message. He said that the problem was a buildup to carbon dust coming from the brushes in the autopilot linear drive motor. He was able to correct the problem by disassembling the linear drive motor, cleaning out the dust, and replacing the motor brushes. The dust was causing the brushes to make intermittent contact with the drive motor rotor and this caused the intermittent drive motor failures.
I disassembled the autopilot linear drive but found relatively little dust in the motor. I was not sure how much dust was required to cause the problem, but it seemed unlikely that was the problem. With some difficulty I reassembled the drive motor and tested it to ensure I had reassembled it correctly. The motor appeared to work so I apparently reassembled it correctly, but I doubted I had found and fixed the problem. I tightened all of the autopilot electrical connections, but none appeared loose.
Ron, Joan Marie, and I took the boat out for a two hour autopilot test run. The autopilot worked for the entire two hours which was encouraging, but hardly conclusive, since the earlier failure only occurred after four hours.
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