[CA] [CA11] ST6002 and 400G AST system

[Deekay911]

Hi, I bought a boat recently with the ST6002 and 400G AST course computer autopilot. I believed it to be working, but it has an issue. After a couple of minutes on auto, the boat's heading clearly starts to wander and after a short while the ST6002 beeps and shows 'STOPPED' and returns to standby. I tried doing the sea calibration but that didn't help at all. I know this is an old system now, but you still see plenty of these around working great. I am tempted to buy a course computer on ebay for $500 and swap it out to see if that is where the problem lies, maybe even the head.

Any clues on how to troubleshoot this, or isolate a component? If i bite the bullet and scrap the system, is there any upgrade path that could keep some of the existing setup, say the wiring, the rudder drive motor (hydraulic), rudder sensor etc?

Any comments would be most welcome! Thanks!

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Deekay911,

The most common components to fail in these systems are the autopilot's fluxgate compass or the autopilot course computer's gyro. One may determine whether the rate gyro (see photo below ... there were a couple of versions of this rate gyro, so its appearance may vary) is responsible for the reported symptoms by simply unplugging cable from the course computer's processor board and then testing the performance of the autopilot. Replacement rate gyros are no longer available and operating the autopilot without a rate gyro would simply cause it to function as a non-gyro assisted autopilot. Should the problem persist with the rate gyro disconnected, then it would be recommended that the autopilot's fluxgate compass be tested per the FAQ found here and replaced if found to be faulty.



If seeking to update the autopilot, please note that the currently installed rudder reference transducer and drive unit may be retained for use within an Evolution autopilot system.