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I had a similar problem with my 91 beater truck. It turned out to be a broken ground going to the cab.
Duralast Gold... Autozone... not the greatest. Bring it back to them and have them bench test it. I've had several "new" ones fail very soon after installation. I take a chance on alternators but anything like starters I go to a real auto parts store like NAPA and get the good stuff.
Boulky12 It sounds like a loose connection at the Alternator or broken or shorted wires leading to the Alternator.When you find out exactly what is going on with those wires please post again it will help me and others.Thanks Ron