Plain Jane wiring harnesses made specifically for your application are available from many vendors for less than $150 bucks or so.
It will be easier and safer to rip out all of the old wiring and installing the replacement harness. This is taking into consider your admitted lack of "experience with electrical work".
There is no need to try to learn what the last guy did wrong. His grounding of the ammeter lead is enough information for me to conclude not to trust any thing else in the system.
bartamos has given you an extensive list of items to help you along the way in terms of what to look for. (Don't let his uppity Arizona Rancher facade fool you. He knows his stuff.)
Carl
cattle flatus intermediator
Last edited by 52Carl; 02/12/2019 12:21 AM.
