I would start be checking the fuses in the power distribution center, give them the wiggle test while the engine is running to see if the charging system responds. Next I am assuming you installed an AC Delco alternator becasue other will just fail. That's been my experience anyway. Next, check the battery and alternator wiring for corrosion.
There is a battery/alternator control module that might be bad, I have included some wiring diagrams so you guys can start looking and testing to make sure there is 12 volts where there should be.
Check out the alternator wiring diagrams below
Please run some tests and get back to us so we can continue helping you.
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Thursday, May 13th, 2021 AT 7:53 PM