Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, proposed preliminary tries (if have not been done):
All others would be internal.
Please consider 'Feeder wires'; i.e. magnet wires with stripped ends plugged into the battery connector to provide test points even with the battery cover in place.
Tomorrow or when able, please post back with clear pictures of the "...battery cover...battery cover switch.."