[CA] Type 400 S3G course computer only works in the tropics!

[MingoMike]

My course computer works fine when it's in the tropics, but not in colder temperatures. Seriously.

After powering up and activating the autopilot, the drive freezes position for 10-15 seconds, then the controller displays a current limit error. Hours later, it starts working normally and continues indefinitely in a normal state. After this failure, if I warm the controller with an electric heater, it returns to a normal working state. Also, if I pre-warm the controller with the heater before powering up the system, the computer functions normally at startup. Systematic troubleshooting eliminated other causes, including removing and bench-testing the M81131 Type 2 short drive.

Is this a familiar problem with a predictable fix, or is it really as weird as it sounds?
Assuming no predictable/reliable fix, what are my options for (hopefully plug-and-play) replacement?

Specs:
Course Computer 400 - E 12055 0520152
with post-manufacture notes indicating
"(S3G), "Added Rate Gyro Processor in 2012" "software updated to V 4.19"

Other system components:
C80 MFD (have E80 ready to install to replace C80)
RD424 Radome
ST60+ Wind
ST60 TriData
ST6002 Controller
Raystar 125 GPS

Thanks, Mike

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Mike,

Please click here to view a FAQ addressing this subject. Should the fault be determined to be rooted in the autopilot course computer, then the autopilot course computer would unfortunately need to be replaced, as Raymarine's Product Repair Center can no long provide service for the SmartPilot autopilot course computers (S1G, S2G, S3G).

If considering replacement of the autopilot course computer with an Evolution autopilot, then the T70161 EV-400 Sail would be recommended. The Evolution autopilot components will be interfaced to one another via the SeaTalkng backbone included with the kit. The currently installed rudder reference transducer may be retained for use with the ACU-400. As the MFD is an E-Series Classic MFD, should its software be updated to v5.69, then the MFD will support SeaTalkng/NMEA 2000 communications. It may then be disconnected from the SeaTalk bus and instead interfaced to spur socket within the SeaTalkng backbone via an A06061 E-Series Classic to SeaTalkng Spur Adapter. Should a SeaTalk to SeaTalkng Converter be added to the SeaTalkng backbone, then the other unpowered SeaTalk devices which you have listed (i.e. ST60+ Wind, ST60 Tridata, Raystar 125 GPS Sensor) may be interfaced to the system. The ST60+ Wind, ST60 Tridata, and Raystar 125 GPS Sensor will be powered by the SeaTalkng backbone via the SeaTalk to SeaTalkng Converter.