Welcome to the forum.
A document search did not reveal the wiring diagram for that boat.
On my 2000 380DA there are local helm buss bars for ground and earth. There is also a local circuit fuse panel for helm electronics.
When I did my custom electronics, in addition to a high current fuse feeding the autopilot, I also used a low current fuse for the small circuit I made for the autopilot on/off switch, so the rocker would have the correct on/up, off/down orientation.
In my case, both autopilot fuses are at the helm fuse panel. Maybe yours is similar.
On my boat, all those electronics were installed after leaving the factory. The original electronics installation workmanship was functional, but sooo far below my standards. When I upgraded the electronics I removed every single cable to redo the installation to my standards, even for components that were being reused.
I also made a custom wiring diagram for everything I did on my boat. Also, every wire / cable is labeled at each end, to aid in future service.
Here is a wiring diagram example:
https://live.staticflickr.com/65535/48111080478_7c691a046f_c.jpg
