Don't know about yours as I am not familiar with that brand however some of the early
small boat autopilots did not have
fluxgate compasses as do the modern ones, they had a magnetic compass which turned a drum through which a light shone to a light
sensor. The drum was marked with a gradually darkening surface. As the heading changed the amount of light passing from bulb to
sensor through the drum varied and this was used to control the drive for the
rudder. If you carerfully remove the cover on the control
head you may be able to see whether this is so or not. Not sure where yo go from there though.