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A/C Not blowing through upper vents when selected

- Chevrolet-TrailBlazer
Forum Post
04/23/09 19:17
M Brannon

A/C Not blowing through upper vents when selected

I love my '07 Trailblazer, but the a/c does not blow through the upper vents when selected by the controls, the air comes out at your feet. It will come out at the defrosters if you select that also, but the vents are a no go, and yes, they are all open. Are they vacuum valve controlled, where I may have a line that came loose somewhere or is there a fuse that controls the selector flap that may be blown. Please help I'm in Arizona and it's starting to warm up here! My model is a top of the line LT with the climate control t-stat type controls. The temps are okay, heat and cold, just the location.
Archived Replies

This post has a total of 43 replies. The most recent 25 are shown below, you can view the complete archive here: A/C Not blowing through upper vents when selected archive. Your feedback, comments, opinions and questions are welcome and encouraged.

This forum post has messages dated from 04/23/09 through 09/26/13, please be sure to read all the messages. If you feel it is old or outdated, please follow up with a question or comment and someone may be able to update it, or reply with newer information if you have it.

19
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adrian

See the link...this guy seems to know what he is talking about and responds very fast to postings
20
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Evan

Just an FYI. I have the same problem with my 99 chevy astro van. Ac works through the defrost vents but not the others. I dont know why.
21
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c parish

I have the same problem with my 04 trailblazer ... The problem started when battery died. So it may have somethin to do with the battery not sure? but this is ridiculus chevrolet needs to issue a recall and fix all of our vehicles!
22
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Rhonda

I work at an automotive repair facility. We have a 2004 chevy trailblazer in here for a/c just blowing out the floor vents. I just talked to a good friend that works at the dealership. They said that one of 2 things could be wrong. The battery was changed recently & the HVAC head wasn't reprogrammed or the mode actuator needs to be reprogrammed. They now have updates to both of these. They need the new update to function properly. Hope I helped. They also told me that it would cose about $100 for the 2 updates.
23
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Jaffar

TrailBlazer 04

if I stopped ac not working probably

24
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Diana

I am having the same problem with my 2003 Chevrolet trailblazer. My a/c was working fine. The battery had to be replaced. After replacing the battery the a/c would not come back on. We are under a heat advisory and I need a/c in my vehicle... HELP
25
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Bonnie

the same thing happened in my 03 tb...just changed the battery ac is cold and works but not on upper vents
26
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Rob

I am having the same problem. The AC works but only through the defrost. It seems the control function of the vents is in op. I am going to pull the lower dash in the morning and will post my findings in the AM. I have seen this problem before and it was a pen stuck in the flap, must of slid down from the vent when someone used the vent for a pen holder :) I did it myself in a 2003 chevy 2500hd.............
27
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Denise

my chevy T.B 03 ac stop working after i change battery also took it in and was told that the digital throttle was dirty and needed to be cleaned
28
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jerry

the problem is could be a few thing behind the control knob there will be like six vac hoses under glove box is were they go check if you have vac going to switch
29
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al doering

talked to my guys and said this is a difficult fix.some cases require lifting body from chassis.good luck.i own a 2003 trailblazer ext lt.2nd time i'll be putting in cooling fan in 2 years
30
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GILBERTO MAISONAVE

Trai blazer doesnot used vacum to control air condition instead is a eletronically controlled. start replacing the control unit located under the radio. Unfurnately it could be also problems with with doors inside the the ventlation sistem.
31
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Dave Kouba

"01" Chevy Trailblazer: While pulling a hill or accelerating cold air comes out of all vents. Seems to do ok as long as engine runs constant rpm.
32
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Ed Ventura

I have 2003 trail blazer LT, got the same problem since i have it brand new, AC is not working properly, outside air is coming in, so you smell the smoke from outside, bottom line is i will never own a car like this, i have encounter other problems not only this, sucks
33
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alexander

Changed the battery in my 02 TB, they dont tell you, you have to do it in less than 5min.. any thing longer than 5min. the computer forgets everything, ie. how to idle with a/c on, how to idle (ssmoothly) with the a/c off, and last but not least, how to change from floor vent to dash with the cold air. I was also told dirty throtel body, "clean it, and it will remember it's setting in a couple of days", a month ago. I realy think it's in the resetting of the computer, but who knows how??
34
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regbert

I'm having a similar problem on the '97 Mazda Protege that I just bought. Air thru all vents except the center vents. These have no open/close button. I've read all these posts about the Trailblazers doing this after the battery has been disconnected. I know the dealer put in a brand new battery, so I'm wondering if it could be a similar issue. Anybody have this issue with a Protege or other Mazda model?
35
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Ephrata, Pa
Thank author of this post/comment"blower, a / c"

I have the same issue where the blower wasn't working for my front levels. After thinking that the "blend door actuator" was bad, turns out it was actually working. I just got jammed up. Then we discovered that the climate sensor was showing -40 degrees outside when in fact it was hot as hell that day. I read somewhere that the sensor is behind the grille in front of the raditor. It might be dirty, or just need replaced. I saw all these parts on Rockauto.com for realy really cheap compared to advance auto and those chain suppliers. I will check the sensor and post it here if that's the issue...
36
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Space City USA
Thank author of this post/comment"One possible solution to TB a / c issue"

Well like the rest of you, I changed my battery and cold air stopped blowing thru the middle front vents. I did some research and I came up with a solution that worked for my 2004 TB LT...being that most TB manufactured after 2002 are all electronically complex they require a great amount of voltage to operate the computer properly...the original battery was fine of course until it died, but the specified battery that the was given to me to did not posses enough power. The a/c system requires more energy than all other systems combined, if you find (like i did) that all your mechanical components (flap motors, vacuum hoses, mode selector) are in good condition then the answer is you have to upgrade your battery beyond what retailers now specify as the correct battery. Go to a heavy duty battery with at least 750 or more "cold crank amps"...then drive your car for at least 50 miles to reset the computer and it should fix the a/c problem...good luck!
37
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Las Vegas
Thank author of this post/comment"Vent Issue"

Having the same problem as everyone else...In response to the last message, the new battery I got has 800 cold crank amps...Just driving with this will make the computer reset?...I know nothing about cars and am very angry that this happened after replacing the battery...Any help from ANYONE will be greatly appreciated
38
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Ephrata, Pa
Thank author of this post/comment"vents"

After having all kinds of confusing issues with the vents. Turns out after a few hundred dollars, it was only a freakin relay worth $15!!!
39
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baton rouge la
Thank author of this post/comment"trailblazer"

if you start your trailblazer and when its running hold the key down like you are trying to start it again and hold it there the limited slip light and brake light will come on when that happens its resetting your comupter hild it for a few more seconds and you should have front vents again it worked for me
40
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Tyrone, OK
Thank author of this post/comment"2004 Chevy Surburban, no air coming out of upper vents."

I have a 2004 Chevy Surburban. I just removed the insturment cluster to send it off to get rebuilt. I am using my GPS for the speedo. I tried to use the heat today and found out that air is not coming out of the defroster or the upper vents. It comes out at the floor though. Can any one give me an idea if it is related to the cluster being out or is this another problem and how do I fix it or what do I check to see if anything is disconnected.
41
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United States
Thank author of this post/comment"81 MonteCarlo A / C problems"

A/C stuck on lower and defrost areas. The controls don't change the a/c blowing areas, just starts and stops system. Anyone know a site w schematics for older chevys. Also the high fan wont engage, I have one speed for blowing...I need a A/C car geek to come to the rescue here...please.
42
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United States
Thank author of this post/comment"i fixed the vent problem on my 81 MonteCarlo"

I found the vent duct door, it was rusted. I pushed it up to block off ddefrost area. It worked, its now stuck on the front vents, where I want them. It wasn't difficult at all....lol....
43
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Indiana
Thank author of this post/comment"2004 trailblazer air vent problems"

What was the relay you replaced and where is it. I have had everything out of my dash trying to find the problem with no luck. Tried all the suggestions except yours.. Thanks Carl
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    Archived Replies

    This post has a total of 43 replies. The most recent 25 were shown above, you can view the complete archive here: A/C Not blowing through upper vents when selected archive. Your feedback, comments, opinions and questions are welcome and encouraged.

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    Chevrolet TrailBlazer 'A/C Not blowing through upper vents when selected'