Vents on the ceiling of the trailblazer

SOURCE: No air blowing from the dash vents

sounds like you have a vacuum problem

SOURCE: Air Conditioner blows hot on one side after battery DC

You need to replace the driver side temperature door control actuator. While doing this... make sure you bolt the new one in AND THEN PLUG IT IN or it will spin and not line up in the right place... then there is a series of crazy steps to fix that problem.

SOURCE: I changed the battery in my 2004 Chevy Tahoe

I recently had the same problem with my 04 Silverado 2500HD after I replaced the battery. I am guessing that you have dual climate contol. You need to reset the climate control. I reset mine by simply shutting the AC off when truck is running and parked. Then turn off the truck
and pull the AC and HVAC fuses out of the fuse box. Leave them out a few seconds and put them back in. Start the vehicle and leave the AC off for about a minute, then turn it on. This should fix the problem. If not, try it again. If still not, you might have to do the same thing except unhook the battery at the same time you pull the fuses. Good luck.
It worked for me.

SOURCE: My vents on my 2004 Chevy Trailblazer won't blow

Hi
The vents only direct the air - the fan blows the air.

Try looking for or having a mechanic look for a blown fuse this is the most common problem.
Thanks and best of luck with it.

Harvey N Tawatao

• 3854 Answers
• Posted on May 08, 2010

SOURCE: Air will not blow out of dash vents on 04

Pull the HVAC B fuse located inside the truck for 5 min and then place it back in.The short time the fuse is out and placed back in, the control module will attempt to recalibrate all the actuators, by running them CW and CCW until they hit their stops. Then the control module remembers those positions and tries to not slam the actuators into the endpoints with vigor, to avoid breaking them.
Naturally, they messed up the programming, and the recalibration process is what breaks most of them after a battery discharge or swap.
When a recalibration fails, the control module just quits using that actuator and it's frozen in position. All the other ones are OK, though. What some Trailblazer owners do as a temporary solution, is to start the recalibration process with the fuse pull. Watch the actuator until it's in exactly one position that is useful, and then quick like a bunny yank the connector to that one actuator. It might be frozen in position, but you can choose a good one. The same trick is a lot less useful with temp actuators.
Thank you for using Fixya and might be a dead airflow mode actuator. Common problem.http://forums.trailvoy.com/attachment.php?attachmentid=505&d=1208022408