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Why is my autopilot showing errors?

2021 January 1

Dear Boat Doctor,

I am having some problems with my Raymarine autopilot. It’s an older unit and worked great right up until it didn’t. It’s a ST6000+ control with a Type 300 computer and a Type 2 linear electric drive. I am getting an error stating “Drive stopped.” I am not sure how to diagnose my problem. If I need to replace it, can I reuse any components?

Walter Pfeiffer

San Diego, California

Dear Walter,

Your autopilot is telling you it has a problem, and that’s good news. Let’s walk through each subsystem.

The error means that the computer detected that the drive is not moving and that it has stopped trying to send power to it. Start by checking the wiring between the course computer and the drive. You will see a relatively large single pair of wires between the devices. If there is an open or corroded connection, that could be your problem.

If the wiring looks good, you may have a drive problem. The drive is relatively simple, it’s just a DC motor with some gearing to make linear motion. You can apply 12 volts DC to the input leads and the drive should move. If you reverse polarity on the leads the drive should move in the other direction. If the drives moves in both direction, its likely OK.

If the wiring looks good and the drive moves, you likely have a course computer issue and that’s harder to diagnose or fix. You’d be looking at a replacement in this case. If you need to replace the computer, you will need to replace everything but the drive and the rudder angle indicator. 

Raymarine changed things dramatically in the last few years. The new control heads will only interface via NMEA2000, known as SeaTalkNG in the Raymarine world. You will need a new control head and the network cabling to connect to a new computer. The functionality that used to be in the course computer is now split between two devices. The Actuator Control Unit supplies power and controls the drive. The Sensor Core is a very sensitive course computer measuring pitch, yaw, roll, heading, course and more.