where is the ac drain line on 2004 trailblazer

on the firewall...if your talking about the evaporator drain tube.

Carefully jack up and support the right front of the vehicle, crawl underneath and look for the evaporator drain tube pointing downward at the street. It's usually made of rubber, removable, and pulls off easily.

Also see other post.

can anyone post a picture? I am a visual learner. thanks!