2001 s10 blazer battery light came on and gauges went crazy and it stopped running,put in new battery and it won't start. thought maybe alternator is junk, but I figured the new battery would have at least started it. also fuel gauge reads empty but I know there fuel in the tank because I added some. anybody have any ideas.

 

I'd pull the alternator and have it bench tested at AutoZone (free service). Also, now would be a good time to check and/or replace the battery cables. I once had a Ford truck with battery cables that looked fine on the outside, but were corroded on the inside, thus causing a no start problem. Installed new cables and that truck came right back to life. Good Luck.

 

I had an '87 pontiac that did the same thing then died while after trying to accelerate from a stop. Turned out the ground wire from the battery blew out causing all sorts of shorts making the dash go crazy. Car ended up dying cause of a blown fuel pump fuse, no physical damage (besides the wire) luckily.

Moral of the story, check your battery cables like junkmonkey said, and check from blown fuses

Good luck!