On mine its hotwired, and when the circuit breaker is on it goes right into standby without a switch. Mine is also 2006 and has been trouble free.
I guess you can call mine "hotwired" too, since there was no on/off switch I just hotwired it directly to the 'instruments
' button on my circuit breaker panel thereby creating an on/off switch. As soon as I push the circuit breaker button the Autohelm control head comes on in "Standby" mode
I would try finding the wires for the control panel on the back of the unit and follow them to the ends and see if/where they are connected. There will be several sets, one going to the steering mechanism, another to the fluxgate compass, and another going to the rudder sensor setup, and they all look the same, so it may be prudent to see that they are all hooked up. If I recall I think the back of the control unit is labelled where each component is to be wired so it should not be too hard to see which ones are connected to it.