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Vent system

Tiny
NORSKI441
  • MEMBER
  • 2006 CHEVROLET TRAILBLAZER
Why would air not blow through the vents in the dash, but will blow through the defrost and floor vent?
Tuesday, July 5th, 2011 AT 11:20 AM

14 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Because one or both of the actuators on the hvac unit aren't working right. They could be stuck or not working at all. Trailblazers were also notorious for the control head going bad. I'll send a generic pic of a hvac so you can see where the actuator is.
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Wednesday, August 23rd, 2017 AT 4:31 PM
Tiny
DBOOGIE
  • MEMBER
  • 3 POSTS
  • 2004 CHEVROLET TRAILBLAZER
  • 71,000 MILES
Recently my front vents stopped working on my 2004 Chevy Trailblazer. I've tried to recalibrate by taking out the fuse, waiting a couple minutes, putting the fuse back in, turning the car to run, letting it go through its motions, but that didn't work. The air blows cold, but it is only coming out at the feet, side vents and defrost. Do you know what could be the cause?
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Saturday, June 20th, 2020 AT 10:49 AM (Merged)
Tiny
PROMECHANIC
  • MECHANIC
  • 536 POSTS
It sounds like you have a mode door actuator that has gone out. Here is a guide that will show you which actuator to replace with diagrams below to show you on your car.

https://www.2carpros.com/articles/replace-blend-door-motor

You can try: Turning your key on and pull fuse 39 under the rear seat. Wait for a minute and put it back in. Let it sit for couple of minutes and restart the engine, might be good to go. Here is what it will be like on your car. Please let us know what happens. Cheers,
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Saturday, June 20th, 2020 AT 10:49 AM (Merged)
Tiny
DBOOGIE
  • MEMBER
  • 3 POSTS
Ok, thanks for your help! I will try that!
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
PAULCOBBLE
  • MEMBER
  • 1 POST
We have a 2005 trailblazer that has been having the same problem. We took it back 2 different times within the first year for the same thing. Amazingly when we took it this time they was able to tell me what the problem was. When they took it to the shop to check it the A/C was working correctly. When they called us to tell us what was wrong with it, they said that when it has a problem like that it saves the code. He said that the actuator needed to be replaced $250. When we got back to pick it up I asked why they couldn't get the code like that when we brought it in for that 6 yrs ago. He couldn't give me an answer.
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
BIBLIA23
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 4WD
  • AUTOMATIC
My air conditioner only blows the air through defrost or bottom vents, but none through the front, what could it be?
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
When you select center what happens?
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
The mode doors are controlled by an electric actuator mounted on the driver's side of the HVAC unit under the dash. The actuator may be bad or the linkage may just be stuck.
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
KELLY SELTZER
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 169,900 MILES
The air conditioner is blowing cold and hot at the same time, cold on every vent besides the passengrer side. The air is cold so I know it is not the freon
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
There is a blend door in your heater and it's either stuck or not working. It 's electrical or vacuum. You can reach your hand under the dash and see if you can move it one way or the other. You should be able to see if it will start to put the pass vent cold or not.
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
DTLAXSON
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • V8
  • 2WD
  • AUTOMATIC
  • 60,000 MILES
Hello,

My problem is the dual electronic controls work on all but the top vents when in that mode. Also when the unit is off it still blows on the floor. Thanks Troy
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Does it still blow (fan on) or is it just outside air getting in? Pretty sure those are a constant air circulation truck, there is always air coming in. The controller wont switch to the dash vents?
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
ELIZABETH CIANO
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 176,000 MILES
Where is the fan speed resistor located?
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Behoind glove box in air plenum just left of blower motor
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Saturday, June 20th, 2020 AT 10:50 AM (Merged)

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