amp guage issues need help

For sure bypass the ammeter inside the engine bay. You don't require the ammeter or a voltmeter. My modern Chryslers have neither, though on trips I stick a cig lighter voltmeter in so I am not flying blind and get stranded (been there). I posted a way to keep your ammeter active, even w/ >100 A alternator, but beyond the abilities of most here.

But, unless the thick black wire itself shorted, your problem is somewhere else in the wiring (probably dash, but could be engine bay) and will bite you again if you don't find & fix.