Air flow

I have a 2003 chevy trailblazer and the air comes out great at the feet but has quit coming from the upper vents. Can anyone tell me what I need to check and how much it may cost? Thanks


I have heard of this in other TB forums, usually after having a dead or replaced battery, and one solution that works for some people is resetting the computer. You will need to disconnect the positive battery cable for 30 seconds or so to do that. Your engine may take a little time to relearn how to run but as a free, if you can do it alternative, it is worth a shot.

Air flow is controlled by flaps, or doors, within the heat/AC system. If these flaps don’t move correctly you can have heat when you want cold, or floor vents when you want dashboard vents.

These flaps may be controlled by vacuum or electric motors. I don’t know which your vehicle has, but I’m sure someone else will know.

Keep checking back for more information.

What you need to check? This is simply beyond your skill, experience, and aptitude; unless, you can get the repair manual and follow the instructions on going into the dash and checking the A/C ducts and door actuators. Most of the cost will be for the diagnostic time; and that’s not easy to estimate.

Saw these after looking further

The purpose of this service bulletin is to announce the release of a new essential tool to service the Heating, Ventilation and Air Conditioning (HVAC) Mode Door Actuator. The new tool is an HVAC Puller, special tool number GE-47676, which was shipped in the Fall of 2004 to all Chevrolet and GMC dealers. It will no longer be necessary to replace the entire Mode Door Cam Assembly when only the Mode Door Actuator requires replacement. Previous to the release of this tool, it was necessary to remove the entire Instrument Panel Carrier to replace the Mode Door Cam Assembly. Now the Mode Door Actuator can be serviced from underneath the left side of the Instrument Panel Carrier using this new special tool.

I was having the same issue with my 03 Envoy with manual HVAC controls. Air only blew out of the defrost and floor vents no matter how what setting I put it on.

I tried the reset process with no results. I did notice this, when I removed the HVAC b fuse and turned on the fan, it would cycle through the dash vents for about 5 seconds then blow out of the defrost and floor vents.

I was able to fix this be replacing the mode door acuator.

ACDelco part # 15-73596
GM # 89018657
cost was $37 from a parts store

It was a pain to replace it but. Fist you have to take the bottom cover from under the dash on the drivers side. I also removed the plastic floor air channel. If you get on your back and look up, it will be to your left. There are two acuators and the look almost alike. You want the one that is to the right. It took about 1 hour to do and like I said, sort of a pain, but well worth the $450 I saved.

Hope this helps someone.