To me it seems like you probably just have a loose ground wire or battery terminal. Or maybe you just need to clean the terminals.
How to clean terminals -
https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked
If that is not it, then follow those cables to wherever they go and make absolutely sure that the connection surfaces are very clean and tight. Dirt and/or looseness will cause all sorts of problems.
Let us know what you find.
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Thursday, September 27th, 2018 AT 1:02 PM