The thin wire usually gets attached to the solenoid and is the wire that comes from the starter switch. However if that wire is already connected and the wire in question has a large enough lug on it then it could well go on the main terminal and supply some other source with a live feed.
Answers & Comments
The thin wire usually gets attached to the solenoid and is the wire that comes from the starter switch. However if that wire is already connected and the wire in question has a large enough lug on it then it could well go on the main terminal and supply some other source with a live feed.