how to clear ac drain line on 2004 trailblazer

why do you want to clear it? is it blocked? Start with where the AC evaporator housing, usually located below the glovebox, then find a rubber tube going from there through to the floor. Double check it is the right tube underneath the vehicle

Pressurized air is the preferred method to clearing it.

Theres a cap with a drain hole that a short removable line comes out. It all fits over a hard 1/2'plastic tube.. the cap slides off and watch the water run! the clog was in my cap. i did run a tube up in to the pan and flush it with bleach water,, all came out clear.