Autopilot p70 "no head' error message

I am having a problem with my autopilot (AP) that produced a "no head" error.

The AP was on standby and the screen went blank. It looked like it had powered off. I tried using the power button but the unit would not turn on. There was very low visibility so I ignored it and turned to determining the correct course and keeping to it.

Then, the AP began to restart showing the Raymarine logo. However, before it could restart the screen would blink or flash and it would turn off again. This went on for a minute or two. Then, as part of the startup sequence it would get a little further and display the main screen but without any data and it would flash, almost too quickly to read the message "no head". Then, back to restarting, failing, etc. I think it did this for between 3 and 5 minutes before the AP turned on and stayed on for the remainder of the sail.

I googled the error message but didn't find any indication of what the problem is. We were not using the bow thruster and we were under power. I'm guessing it is a loose connection someplace and the error message gives some idea of where the connection is weak.

Any suggestions about how to diagnose the problem are appreciated.

Best,
Alan