2003 Chevy Trailblazer V8, Battery replaced.
Question- After having the battery replaced the dash vents will no longer blow air.

I will need a little more info to be of some help. Is there airflow from any vents (defrost, vent, lower)
Is this the automatic or manual a/c system? Any more info will be helpful for me to assist you.

Thanks for your quick response.
There is air flow from the defrost, lower and the back air vents.  The dash vents seem to be the   
only area without airflow. Not sure what you mean by "the automatic or manual a/c".  Sorry. Thanks.

The automatic system controls air temp and delivery automatically, the manual system you must  
control yourself. Sounds like you have a problem with the mode actuator. Sometimes this happens
after a battery is replaced, or after trying to jump start. Fist thing to do that usually   works is
perform a reset and calibration of the mode doors and control head.

With the key off, remove the HVAC B, and the HCAV 1
fuses from the rear fuse block under the   
second row seats. Wait for at least 1 minute. Re-install fuses, start truck and do not touch a/c  
control head for 2 minutes. Shut off truck, re-start and check for normal operation.

2003 Chevy Trailblazer  4.2 ABS light.
Checked codes, none. Took of wheels and brakes and rotors looked fine. Replaced
hub of one wheel a few months ago, not same noise as before though.
Question = I few weeks ago, my ABS light went on. Then about a week after that I
started getting what sounded like a scratching noise ( I thought was brakes but
wasn't). Starting last night, I turned left and it sounded and felt like my axle was
broke or something, horrible thumping noise. It stopped after a few minutes, so
drove a little more and about an hour later it started thumping again.
If the
ABS light is on, then you do have codes stored in the computer. You may not
have a scanner that is capable of reading ABS codes, and that's why it shows no
codes. The noise you describe is probably another hub bearing. And most likely,
that's the reason for the ABS light. You may want to get it checked out by a
professional or someone that has a proper scanner.

Sometimes hubs do go bad without setting a code too, so it's possible you have a
couple different problems. Since the brakes are fine, you can look a little deeper by
turning each wheel independently while you have it jacked up and listen for noise
and also check for looseness of the hubs and suspension components and axles.

Definitely needs some looking at.

2006 Chevy Trailblazer.
Question- I went to turn on the fan switch in my car for the air conditioning; however, nothing
happened.  I turn on the rear air conditioning and that works fine.  Does this mean the fan motor
went or is there a problem with the fan switch?
The blower fan problem could be several things. The actual switch in the dash
control panel is not very common. Most common is what is called the blower
motor resistor module. This is what control the speeds set by the switch. They
tend to burn out. Sometimes when they fail, your truck will only have high speed.
That is the first thing to check. It is located under the passenger side of the dash.

The blower motor is less common, but could still be the problem. You would need
to do some electrical testing to determine which one has failed. Or remove the
resistor and look for signs of being burned or melted.
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Chevrolet Trailblazer Heater / AC and ABS Problems
Chuck said:
Re: "2003 Trailbalzer V8, Battery Replaced", Question where dash vents no longer blow air. I have exactly same condition on my 2003 TB, although
6cyl. Performed the reset & calibration procedure exactly as described. No result. Cannot place origin of problem to battery replacement or other
action, but condition has been for months. Any additional remedial suggestions would be greatly appreciated. (Manual system).

Anonymous said:
@Chuck,You have a bad mode door actuator. Just like with the temperature door actuators, there is also one for switching modes from floor to vent to
defrost. See this link...