air only from defrost vents

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air only from defrost vents

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Chevrolet >> Chevy Trucks, Vans & SUV's >> Suburban >> air only from defrost vents

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air only from defrost vents - 8/5/2007 11:00:40 AM

wareagle72

Posts: 1
Joined: 8/5/2007
Status: offline

Hopefully you guys can help.

I recently had the battery changed on my 2003 suburban and now the air only blows from the defrost. When i start the car up it cycles through the floor board, then the normal "face" vents and then ends up only blowing from the defrost. It does not matter what i change the air flow position to (feet, face, defrost).

Any suggestions?

Post #: 1

RE: air only from defrost vents - 1/13/2008 6:08:36 PM

absoffthewake

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

did you ever fix this problem? I have the same problem on my 04 Trailblazer LS

(in reply to wareagle72)

Post #: 2

RE: air only from defrost vents - 1/13/2008 11:21:03 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: air only from defrost vents - 1/22/2008 7:25:50 AM

Z71Guy

Posts: 1
Joined: 1/22/2008
Status: offline

Thanks for posting, you saved me $$ and time! I had the same problem and thought it was the control module, but when I put in a new module it did nothing. So, I did an internet search and found your posting. Then I went out and removed the servo unit (not the easiest thing to do!), opened it up and found that the main gear was cracked. I returned the control module, bought a new servo and we are back in business! Thanks again.

(in reply to absoffthewake)

Post #: 4

RE: air only from defrost vents - 1/22/2008 8:41:40 AM

absoffthewake

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

Isn't the Internet a wonderful thing! I wish I found my post before I started. It would have saved me a couple of hours work too!

(in reply to Z71Guy)

Post #: 5

RE: air only from defrost vents - 3/4/2008 4:54:10 PM

mackiecfx16

Posts: 3
Joined: 3/4/2008
Status: offline

can someone tell me how to take off the servo

i have a 1998 suburban 1500 2wd

and my ac vents only come out from the front and it isnt cold

it will also not switch back and forth between defrost and main vent

can you please tell me how to take the servo off or somthing

or show me a picture

thanks

(in reply to absoffthewake)

Post #: 6