Just had first electrical issue with my 2004 silverado 4wd, 5.3l auto.
insert the key, turn to first position, lights, radio & dash lights come on,
next position, all goes black, a slight buzz under the hood, some times a click.

I took the batery cables off to check for corrosion, none present.
I checked the secondary connections, all tight no corrosion.

the battery is fully charged, have any ideas?

 

Even though the battery seemed fully charged, the battery was shorted out internally.
it has power for the dash lights & radio, once you turned past the accessories the battery would act completely dead.

A friend noted that a few years back, he had the same issue with a battery.
I got suspicious & decided to try a battery swap, new battery now every thing is fine!

 

well, alls well that ends well