ok, what caused it to go bad?? is it bad and how did you check it??

why did you replace the battery and alternator.

Roy
Read this guide on testing wiring, it will help

https://www.2carpros.com/articles/how-to-check-wiring

Since you gave no specifics, we are not able to locate what diagram you need, attached below you will find all of the power distribution wiring diagrams