only floor and defrost vents work 03 T B - Chevrolet Forum - Chevy Enthusiasts Forums

only floor and defrost vents work 03 T B

Join Date: Jul 2007
Posts: 1

July 20th, 2007, 6:40 PM   #1  
only floor and defrost vents work 03 T B

Hello Everyone...I have a 2003 Trail Blazer and my heater\AC vents do not work properly anymore. When I have the rotary vent selector dial all the way to the left position, I should have air blowing out of the middle dash vents. But, air blows out of the floor vents only. As I dial clockwise, the next position is floor and middle vents. Only the floor vent blows air. The next postion is floor vent only and that works fine. The next position is floor and defroster. That works fine. The last postion is defrost only, and that works fine. In other words, I cannot get air to blow out of the middle vents no matter the setting. Any help would be greatly appreciated! Thanks...Greg

Join Date: Jan 2008
Posts: 6

January 13th, 2008, 8:07 PM   #2  
RE: only floor and defrost vents work 03 T B

did you ever fix this problem? I have the same problem with my 04 TB.

Join Date: Jan 2008
Posts: 6

January 14th, 2008, 1:20 AM   #3  
RE: only floor and defrost vents work 03 T B

I Figured this one out!

The problem is with a servo that opens & closes the flap that redirects the air. It is located directly above the accelerator pedal (there's 2 identical servos).What happens is when the computer recalibrates the servo to find the min & max servo travel, it puts alot of stress on the gears that control the servo arm when it reaches the min & max of the travel.After repeated calibrations (ie: disconnecting battery) the gear gets pushed away from the toothy portion of the shaft the main gear is connected to, therefore it slips. Becuase the gear slips, the computer cannot determine the min & max travel, so it drops back to the furthest position (where it directs the air to the footwell & defrost).

You can fix this 2 ways.

#1 and probaly most common, replace the servo.

#2, the free way, open up the servo (real easy) & push the gear back into place. Removing & installing the servo is difficult, and requires a small ratchet with a very long arm. Aligning the gearswheninstalling the servo is also difficult. The servo arm has a notch, and the gear has a pin that must go into the notch. Install the servo loosly and get your fingers in there and feel the pin & notch into place. Since the gear's been pushed out once,I guess there'sprobably the possibility of it not lasting as long as new, but its a great way to buy you some time (maybe another 4 years!)

I must say that it almost looks like it was designed to fail.

Hope this helps someone!

Join Date: Mar 2008
Posts: 2

March 6th, 2008, 8:15 AM   #4  
RE: only floor and defrost vents work 03 T B

I have the same problem with my 03 Trailblazer. You said there are2 identical servos which one do you need to pull out or do you have to pull out both?


Join Date: Jan 2008
Posts: 6

March 6th, 2008, 4:28 PM   #5  
RE: only floor and defrost vents work 03 T B

One controls with bottom & front vents & one controls the defroster. (not 100% sure if it is exactly that way). To find out which one is the failed one, look at them, and see which one doesn't move or does not move as much when you cycle through the air vent settings. You will see a black box looking thing, with a whitish shaft that has a slot through it. That shaft should turn.

Join Date: Jun 2008
Posts: 1

June 3rd, 2008, 8:36 PM   #6  
RE: only floor and defrost vents work 03 T B

Thanks absoffthewake from me too! I had searched all over looking for a solution to this. I wanted to give a few more details on finding these servos though.

You will need to remove 2 dash pieces under the steering column. There you will look up from the gas pedal and see two black boxes sitting beside each other. The one closest to the firewall is the one that controls the defroster. The one towards the rear (the hardest one to get to[&:] ) is the one that controls the dash air/floor air.

**After finding this forum and absoffthewake's info, I tore into my wife's '04 Trailblazer. I did a temporary fix. I took a coin (actually used a quarter) to turn the servo manually and I unplugged the controls so that it wouldn't try to move again (although I'm not certain it would). It now blows fine from dash...but you can't change it. That will be okay with us for a few months. This will get us through the hot Texas summer and allow me to fix this when it's more tolerable outside.

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CF Beginner

Join Date: May 2009
Posts: 1

May 15th, 2009, 2:02 PM   #7  
A huge thanks to firstrobo and absoffthewake who replied to this issue. I just did the quick fix of turning the server with a coin and unplugging it. This will get me though the Central Florida heat this summer until I can take the time to replace the motor. Does anyone happen to know a place that I can order the part from or know the actual part number that I can request when ordering it? Thanks again!!!

nomad's Avatar
CF Beginner

Join Date: May 2008
Posts: 19

May 16th, 2009, 4:09 PM   #8  
On May 16, 2009 I discussed the repairs on a similiar thread. Check the other threads. Nomad

nukeantz's Avatar
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Join Date: Jun 2009
Posts: 1

June 8th, 2009, 8:59 PM   #9  
ac through defrosters

I have the same problem with ac only coming out floor and defrost. I have a 2005 express cargo van, where would the servo motors be located in my vehicle?


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Join Date: Nov 2007
Posts: 18

June 28th, 2009, 8:34 AM   #10  
I had this same exact problem on an 03 S-10 crew cab. It was brand new at the time. After being in the shop 9 times to be fixed under warranty. I filed suit under lemon law to get my truck replaced. I ended up turning my truck in and got my down payment back and all my monthly payments back for 1 1/2 yrs. Put about 18k miles on the truck and in the end didn't cost me anything.

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