Cruisair reverse-cycle heat throws "LO / SE" error

LaRea

Wondering if anybody has seen this fault in a Cruisair air conditioner.  Reverse-cycle heat runs fine for five minutes, then shuts down with a "LO / SE" error -- which means the seawater temperature is too low.  Sure enough, when I press the FAN and UP buttons to display the seawater temperature, it shows up as 22 degrees.

The thing is -- this system doesn't have a seawater temperature sensor.  The circuit board has a blue plug for attaching a sensor, but there's nothing plugged into it.  Somehow, the system thinks it has a sensor.  

To "fix" it, I used a wire jumper to short the plug.  Now it's heating fine on this 50-degree Michigan day.  

I'm guessing the circuit board is starting to fail.  Open to other suggestions.  

Ian

There is a factory default/reset function. Have you tried that? Maybe something is panty bunched in it’s control logic.