My alternator went bad, It had a life time warranty
They replaced it, we tested it before I installed it. It tested good
It does not charge in my truck. I have a 97 F350 7.3 tubo
Any thoughts?

 

Did you take a meter and test the output at the alternator when running?

There should be Alternator/generator fuses in the power distribution box under the hood.

Could be a bad ground, batteries, fuses, bad wiring.

Even though the alternator may have passed their load test doesn't mean its good. I'm not sure on your 97 but on my 99 the voltage regulator is internal, it passed the test every time but the regulator was bad and would cause intermittent charge, no charge when warm and over charge at times.

Should be getting no more than 14.5volts at the batteries when running.