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2009
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My guess would be it is the temp door actuator on the passenger side. What I am not sure about is why it would be blowing hot air out the rear vents as I wouldn't think they would be tied together.

What you could try first, and it wouldn't cost you anything is to turn the whole system off and then pull the HVAC B fuse which is located under the rear driver side seat. Wait a few seconds and then plug the fuse back in. Then turn the key on but don't start it and wait a few minutes. You should here the doors moving and resetting. Then start it and turn the HVAC controls on and see if this helped. If not you will have to investigate further.
 

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Thanks for the info. I did try the whole reset thing and I was looking at the actuator while I started the car. I heard the clicking and grinding noise on the actuator and saw the gear attempt to turn back and forth. Now, I don't see it turn at all. I am pretty confident that it is this actuator. As far as the rear vents, this all started at the same time. From what I read, the temperature is controlled by the front passenger temperature and the only rear controls are for the blower motor. So, if the front passenger is hot, the rear vents will blow hot air. I am going to need to purchase the special tool to get the actuator out. I can access one of the bolts. However the other is VERY difficult, almost impossible to access.

Thanks again. Any more feedback is welcomed on this.
 

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I just replaced the door actuator in my TB. It was a pretty simple job. My battery failed and I lost the forward vents. I went on this great site and got all this info to do the job. When the door actuator failed all I had was the floor and defrost vents. I made sure the switch was in the 1 oclock position infact I even marked the old one before removing it .I replaced the new part and everything is working. However I lost my floor vent. When I have the floor mode selected the air is coming out the forward vents. I get a trickel of air when the fan speed is in high out of the floor. When the actuator was out I could manual move the door back and forth to different vents so I now thats not the problem. I watched the new switch run through its modes while switching the control unit so thats working. I tried the pulling fuse method trying to resent the position of the door. I tried installing in in different position. I noticed that there is a "tab" on the door gear that has to line up with the actuator? Can someone PLEASE give me some insight on this. I feel that this actuator is getting the best of me. Thank-you
 

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2004 chevy trailblazer_ls_ext
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Mode door actuator help

03Huggy....Thank you for the pictures and information. Thanks to you I was FINALLY able to locate where this part was. It took me nearly half of a day to find the location, let alone figure out if this is indeed my problem.

My problem is like many others on this site. I have recently replaced my battery. The air conditioning system began going crazy. The car would stall when the ac was turned on. The air would not blow through my dash vents.
After doing hours of research on this site and others I finally tried cleaning out the throttle control. It fixed the stalling problem.

Now I need to order the mode door actuator and install it to see if this is my problem. I'm confident this is my problem after reading all of the posts here.

I will let everyone know how it goes.

I bought a brand new 04 trailblazer in 04. This has been the worst car I have ever had. The issues I have had with this car should not have happened until atleast 100,000 miles or more. With that being said, I am grateful for the people on this website. You guys have saved me THOUSANDS! I have spent more time than money on my car thanks to you!
 

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2002 chevy trailblazer_lt_ext
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It is the mode door actuator. Do a search and you will find a how-to plus you will see the threads that I have started on this. The mode door actuator on the 2002 is tricky because the shaft is pressed onto the actuator itself and according to GM requires a special tool. We were able to do it without the special tool and I explain how in that thread.

Here you go. I found it for you.

http://forums.trailvoy.com/showthread.php?t=45175&highlight=actuator

This would cause it not to blow out of the drive or passanger side vent
 

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2002 chevy trailblazer_ls
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18 Posts
I just replaced the mode actuator on my 02 TB. 03Huggy's description was dead-on. Took about an hour. Thanks for the great article.
 

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This would cause it not to blow out of the drive or passanger side vent
Yes. It will blow out the defrost because there is a seperate actuator for the defrost. The mode door actuator controls just the dash vents or the floor vents. When mine went bad it would only blow out at the floor.

You can reach up and unplug it then manually move it so it blows out at the dash and just leave it unplugged. Doing it this way will give you air out the dash vents until you have time to repair it.
 

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2002 chevy trailblazer_lt_ext
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Yes. It will blow out the defrost because there is a seperate actuator for the defrost. The mode door actuator controls just the dash vents or the floor vents. When mine went bad it would only blow out at the floor.

You can reach up and unplug it then manually move it so it blows out at the dash and just leave it unplugged. Doing it this way will give you air out the dash vents until you have time to repair it.

Not to keep going on the same subject bit right now mine just blows out the 2 center vents wen turned on... If it clicks wit will work fine.... Bt if it does not it will blow out of the far passanger side vent nor the far drive side vent
 

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2002 chevy trailblazer_ls
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18 Posts
If you have the dual zone auto contgrols, there are actuators for the left and right side in addition to the mode and deforst actuator.
 

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2005 chevy trailblazer_ls_ext
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What I am not sure about is why it would be blowing hot air out the rear vents as I wouldn't think they would be tied together.
From what I read, the temperature is controlled by the front passenger temperature and the only rear controls are for the blower motor. So, if the front passenger is hot, the rear vents will blow hot air.
He is right. At least on the EXT the passenger temp. control controls the temperature of the rear vents. I believe it does mention this in the owner's manual, but I'm too tired (and lazy) right now to look it up.
 

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If you have the dual zone auto contgrols, there are actuators for the left and right side in addition to the mode and deforst actuator.
It is the same way for the manual controls also. There is a temp door actuator on the driver and passenger sides.
 

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2002 chevy trailblazer_ltz
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Actuator: done

With the help of previous posts, I replaced the noisy mode door actuator on my 2002. The special GM puller cost $150 from Kent-Moore. Using their illustration, I fabricated one from 1" bar stock by bending it into a u-shape, cutting a slot to go around the actuator shaft, and tapped a 1/4" hole in which to insert a bolt.

I expected a pat on the back from my wife who's the primary driver, but she said she never noticed a problem. Go figure!
 

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2003 chevy trailblazer_lt_ext
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8 Posts
I am a newbie here, but I must say, I am impressed with the amount of knowledge here. I too am having actuator problems ever since replacing the battery in my wifes '03 TB. I did not know where to turn, but have obviously found the right spot. Thanks to everyone for their great input.
 

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2003 isuzu ascender
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I am a newbie here, but I must say, I am impressed with the amount of knowledge here. I too am having actuator problems ever since replacing the battery in my wifes '03 TB. I did not know where to turn, but have obviously found the right spot. Thanks to everyone for their great input.
:iagree: Yup, this one's top shelf for sure! Of all the forums I've participated in over the years related to the car I was driving at the time, this one is heads and shoulders better than any of them. The willingness to help and the sincere concern shown by those who chose to reply to the requests for help is genuine and genreous. :thumbsup:
 

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2007 chevy
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thank for all the helpful info on replacing the ACTUATOR the first time the dealer replaced it & the noise came back a week later & then reading this thread some time ago i took care of it myself & glad to say no noise to date!
 

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2002 gmc envoy_slt
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11 Posts
what about tool for actuator

hay 03 huggy did you need a tool to pull actuator for replacement some say can not get it loose once screws are removed.
 

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2009
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2002's require the special tool. 2003's and up don't. I was able to get mine off without the special tool it just takes a little patience.
 

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HVAC mode actuator reset info

After changing my battery in my 2002 the air would only blow at floor not out of upper vents,after trying all the resets on this board it still did not work.
This is what I did & now it's ok.
1.remove lower dash & vent tube
2.while watching how motor opens door it seems to open upper vents for 5 sec. then blow on floor as you turn key to "ON" (not start)
3. when laying on floor turn key to "on" when air is blowing out of uppervents
disconnect electric plug going to mode actuator.
4.now go to battery or fuse & disc. for 3 mins. & reconnect
5. set mode on air control to show blowing out of upper vents.
6. get back under dash & connect the elec. plug back on to mode actuator.
7. now try changing the air flow using the air control button
8. if it works ok your done...if not see #9
9. repeat steps 1 thru 8
10 this is only for actuator that quit working after battery change
not for broken plastic gears in mode actuator.

hope this helps someone..... John
 
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