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post #1 of (permalink) Old 09-16-2015 Thread Starter
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Front Defrost problems

Hi guys. I have a 2008 chevy Impala LT with the 3.9L engine. This morning I woke up to a foggy morning. Used my remote to start the car early so the Windows would be clear when I got in it. As I was walking to the car I noticed the Windows were not clear. After investigating for a minute , playing with the selector switch , that the only thing not working was the front defroster? It blows out of the vents and at my feet. When the switch selector is in the defrost position it blows at my feet? Any help would be greatly appreciated. Thank you.
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post #2 of (permalink) Old 09-16-2015
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Sure sounds like a faulty HVAC actuator. Seems to be a rather common issues with these cars. You probably need to replace the actuator that controls the route the air takes (forget the technical name). I think that there are like (3) actuators (for dual-zone climate controls). You need to figure out which one controls the airflow path and replace it. They are relatively inexpensive to replace yourself, but can get costly if you take it to a dealer to replace it for you. The part itself isn't much - it's the labor charges that get you.

Do some searches on the forum for "actuator" and you'll find LOTS of details - including the correct part number and replacement procedures.

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post #3 of (permalink) Old 09-16-2015 Thread Starter
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Thank you jtrosky. I will do that right now.
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post #4 of (permalink) Old 09-16-2015
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Before you start throwing parts at it do a "blend door reset"!

Try a blend door reset.
1. Turn heater controls off
2. Remove the TWO HVAC fuses from the underhood fuse center.
3. Wait 5 minutes.
4. Re-install the fuses and turn ignition on. (do not start engine)

This should reset your blend door. If not possibly the blend door controller is bad.
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post #5 of (permalink) Old 09-16-2015
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Originally Posted by Jmac90 View Post
After investigating for a minute , playing with the selector switch , that the only thing not working was the front defroster? It blows out of the vents and at my feet. When the switch selector is in the defrost position it blows at my feet? Any help would be greatly appreciated. Thank you.
If the reset fails to correct the problem, the part numbers for the mode selector actuator are:

GM # 15844095
ACDelco #15-73516

As I recall, this actuator is on the passenger side kinda above and left of the glove box. It can be replaced without removing the dash. Can't recall if I had to remove the glove box.
...

For completeness, there are three other actuators, all the same p/n, for the two temp selectors (blend doors) and the recirc damper:

GM # 15844096
ACDelco # 15-73517

HTH.

Doug

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post #6 of (permalink) Old 09-16-2015
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Kinda curious - why would an actuator ever need to be "reset" to begin with? It it really just an early sign that the actuator is failing?

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Originally Posted by jtrosky View Post
Kinda curious - why would an actuator ever need to be "reset" to begin with? It it really just an early sign that the actuator is failing?
The actuator isn't really getting reset. The software in the A/C controls is relearning the stop points (at each end of travel) for the actuator.

Doug

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post #8 of (permalink) Old 09-16-2015
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There are a few different threads on here about the actuator door motors. It is a common problem if you hear clicking sound in say heat mode only, or if one of the areas does not get any air blowing at all. I test drove a used 07 that had clicking sound and was considering purchasing it. But I did the actuator search on here and found the mentions of the part numbers and Youtube video links replacement on the access through the glove box to get to the motors. I'd do the reset steps first since there are no parts to purchase, if that did not help then I'd get the motor. If there is no clicking then, it still could be a motor problem but could be other issues too (less likely would be a blocked vent, etc.)
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post #9 of (permalink) Old 09-16-2015
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Originally Posted by plano-doug View Post
The actuator isn't really getting reset. The software in the A/C controls is relearning the stop points (at each end of travel) for the actuator.

Doug

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Thanks.

But why would the need to be relearned in the first place? I'm just wondering if doing this is really just a band-aid (and the problem will come back) or if there is a valid reason for someone to need to do this if the actuator is working properly.

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post #10 of (permalink) Old 09-16-2015
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But why would the need to be relearned in the first place? I'm just wondering if doing this is really just a band-aid (and the problem will come back) or if there is a valid reason for someone to need to do this if the actuator is working properly.
If somehow some crud got into the ducts and made its way to the damper, then it could be causing it to stick. The controller circuit monitors the current flowing to the actuator motor. If it see the current jump, it assumes the motor has stalled because it has reached its designed limit travel, and stops driving it, thinking the damper is all the way open (or all the way closed).

A sticky damper will make the controller think it's at the limit when it's not. The stickiness can be a function of temperature. It might stick more on a cold day, for example. So relearning might be a temporary fix until the next cold day comes along.

That said, the actuator's probably bad. But there are indeed other possible causes besides that.

Doug

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post #11 of (permalink) Old 10-25-2017
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Quote:
Originally Posted by Jmac90 View Post
Hi guys. I have a 2008 chevy Impala LT with the 3.9L engine. This morning I woke up to a foggy morning. Used my remote to start the car early so the Windows would be clear when I got in it. As I was walking to the car I noticed the Windows were not clear. After investigating for a minute , playing with the selector switch , that the only thing not working was the front defroster? It blows out of the vents and at my feet. When the switch selector is in the defrost position it blows at my feet? Any help would be greatly appreciated. Thank you.
I had the same thing happen on my 2013 Chevy Impala LT with a 3.6L, I did the same steps as above with the exception being the 2013 does not have the HVAC fuses. On a 2013 you need to pull the fuse for the "Display", you will see it marked on the fuse box cover under the hood of the car. I turned off the HVAC blower, pulled the fuse, waited 5-10 minutes, reinstalled the fuse and turned the ignition to ACC. At first it did not work, I did not hear the actuators resetting themselves, then once I actually started the car I could hear the actuators resetting and everything worked fine.

Thank you all for the help, glad I checked out this site.
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post #12 of (permalink) Old 08-28-2018
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Dude, you're a fricking genius! Had the same issue with my 2013 Impala, tried your fix, and it worked like a charm!
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post #13 of (permalink) Old 02-07-2019
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Just had the same problem with my 2011 Impala and fixed the issue. Thanks you so much, saved a lot of money if I’d have had to bring it into the shop.
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post #14 of (permalink) Old 02-07-2019
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Seems to only work for the mode (vent) actuator?
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post #15 of (permalink) Old 02-14-2019
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Years ago I had a mechanic tell me never to change the outlets (defrost/dash vent/heat) with the blower motor on high, the fast moving air flow creates high loads on the actuators and can cause them to fail.
I always turn the fan down then change the air direction then turn the fan back up, don't know if it really helps but I've never had an actuator failure in this car or other previous cars some of which are known to have actuators commonly fail.
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