I have a brand new alternator in a 2002 chevy trailblazer in the alternator is not charging what can it be

SOURCE: 2002 Chevy Trailblazer Engine Codes

This is actually an easy swap out. Remove the electrical connection, remove the retaining bolt and pull out old one. I believe the sensor is located in the front passenger side of the engine on this particular model.

SOURCE: Alternator and battery

the wire may have become corroded at the starter or shorted out sum where check the wires from the alternator to the battery

SOURCE: locate camshaft sensor 2002 chevy trailblazer

Assuming you have a 4.2L engine here is the location.


Hope this helps out,
if so please rate my answers.
Brett

SOURCE: 2002 Acura Rsx Type S With No Alternating Charge

look at your charging fuse

SOURCE: I have a 2002 Chevy Trailblazer. Just replaced

If you unhooked battery it will need to relearn its idle position, should help if you clean throttle blade edge and body of carbon so proper amount of idle air can enter engine.