only floor and defrost vents work 03 T B

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only floor and defrost vents work 03 T B

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Chevrolet Forums >> Chevy Trucks, Vans & SUV's >> Trailblazer >> only floor and defrost vents work 03 T B

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only floor and defrost vents work 03 T B - 7/20/2007 4:40:51 PM

firstrobo

Posts: 1
Joined: 7/20/2007
Status: offline

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

Post #: 1

RE: only floor and defrost vents work 03 T B - 1/13/2008 6:07:42 PM

absoffthewake

Posts: 6
Joined: 1/13/2008
Status: offline

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

(in reply to firstrobo)

Post #: 2

RE: only floor and defrost vents work 03 T B - 1/13/2008 11:20:33 PM

absoffthewake

Posts: 6
Joined: 1/13/2008
Status: offline

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 gears when installing 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's probably 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!

(in reply to absoffthewake)

Post #: 3

RE: only floor and defrost vents work 03 T B - 3/6/2008 6:15:30 AM

bwaple

Posts: 2
Joined: 3/6/2008
Status: offline

I have the same problem with my 03 Trailblazer. You said there are 2 identical servos which one do you need to pull out or do you have to pull out both?

Thanks.

< Message edited by bwaple -- 3/6/2008 6:16:32 AM >

(in reply to absoffthewake)

Post #: 4

RE: only floor and defrost vents work 03 T B - 3/6/2008 2:28:52 PM

absoffthewake

Posts: 6
Joined: 1/13/2008
Status: offline

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.

(in reply to bwaple)

Post #: 5

RE: only floor and defrost vents work 03 T B - 6/3/2008 6:36:16 PM

RickB68

Posts: 1
Joined: 6/3/2008
Status: offline

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.

(in reply to absoffthewake)

Post #: 6