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Discussion Starter #1 (Edited)
I detached my battery when trying to install HID lights and once I reconnected the battery, the front vents do not blow air or heat. I had read a post that had said to disconnect the battery for 2 mins. then put the key in the "on" position and wait 2 mins for it to reset. I tried this a number of times and had not luck. Does anyone have any suggestions? Thanks in advance!
 

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2004 gmc
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Trailvoys are notorious for having a misdesigned HVAC actuator (used for temp, airflow mode, and so forth) that works just fine until the control module loses its memory when you replace the battery. Then one or more of them mess up during recalibration and have to be replaced.

Run a search for "temp actuator" or "Mode actuator" and read up for a bit. If you're not a DIY kind of person, and take it to a mechanic, do NOT accept any claims that they have to remove the entire dash for $1000 to swap it.

What's gone bad for you is the mode actuator.

 

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Discussion Starter #3
That is crazy! So anytime you unplug the battery, you will typically need to replace this? All other vents work fine. The only ones not working are the dash vents.

Is their a way to make sure this is the problem? Thanks for the help!
 

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Not every time you replace the battery. People have been replacing batteries for years without incident. The GM design team made mistakes, but this one has a delayed effect, so they didn't notice it during testing.

It's just that some of the actuators are poorly assembled, and owners of those vehicles haven't had to replace their batteries, but since you only get 4-5 years out of a battery, they're starting to come here to trailvoy in a relative flood now.

Making sure this is the problem:

1) Go to a dealer whose tech tool can command each actuator to rotate CW and CCW independently.

2) Take the lower dash off as in the posts that give instructions, find the mode actuator, and visually confirm it doesn't move when you change mode, and look at the temp actuator and see that it does move when you change temp.
 

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Pull the HVAC fuse and leave it out for 30minutes and plug it back in start your truck and don't touch HVAC Controls and let it cycle through. It is a common issue. If that does not work, its the actuator Door..

NO Roadie I am not guessing this time......:bonk::bonk:
 

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NO Roadie I am not guessing this time......:bonk::bonk:
Of course not. Except that the fuse-pulling trick is functionally identical to what the OP reported in his first post. (And really, 30 seconds is enough to reset this module, not 30 minutes). And in this thread it's looking like it's a rarer failure of the control module or the wiring instead of a single actuator. But I think we're all agreed in this case (where's RayVoy when we need to build a consensus ;) ) the actuator's design bites. :hissy:
 

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Discussion Starter #7
I am in the process of waiting 30 mins for it to reset. This is my last ditch effort before I pull apart the dash. How much of the dash do I have to take apart and do you have a step bye step process to do so? I know you had mentioned their is a post that has instructions but not sure where. And for future reference, if and when I disconnect the battery, how do I avoid this problem? :suicide:
 

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I am in the process of waiting 30 mins for it to reset. This is my last ditch effort before I pull apart the dash. How much of the dash do I have to take apart and do you have a step bye step process to do so? I know you had mentioned their is a post that has instructions but not sure where. And for future reference, if and when I disconnect the battery, how do I avoid this problem? :suicide:
30 to 60 seconds is all you need to wait. Close your doors and windows and you can normally hear them cycle. I thought I had it, when I pulled the HVAC B fuse, I thought I started getting air through my top vents, but didnt matter, I only got hot air! AC wont turn on with no HVAC B fuse, just hot air from the fan. So had to pull the dash and force the actuator to blow out of my top vents (top vents only preferred over bottom only vents for me and likely most people)

steps from memory:

get under the dash with a light, and a ratchet with a 7mm socket i think it was, get off all those, pull the panel under the steering wheel too, couple of 7mmm or 10mm around there too, lay down on ur back and look up

on your left and up is the temp mode actuator (hot / cold i think) which is easier to see first..

and look up a bit higher and slightly to your right (maybe about even with gas pedal give or take but straight up) youll see a plug with 5 colored wires in another actuator, this is your vent mode actuator (air direction).

i used a flathead to force it to blow out the top vents, just be sure to pull the harness off if you want it to stay that way, until you get a new part (hopefully you dont mind the "check engine" icon lit up on your cluster all the time, cause it will stay on)

oh make sure this is your prob first though, by turning key on and messing with your AC controls. watch the metal round gear, or touch it, and see if it moves when you switch settings. if it doesnt, you found your bad actuator.
 

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PS i added some iphone pics (albeit not the greatest but should help you when on your back looking up into the deep dark dashboard) to the "HVAC Mode Door Replacement" sticky thread
 

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2005 gmc envoy_denali_xl
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That is crazy! So anytime you unplug the battery, you will typically need to replace this? All other vents work fine. The only ones not working are the dash vents.

Is their a way to make sure this is the problem? Thanks for the help!
You can avoid disconecting the battery when you work on the truck; Just don't touch anything that might ground you when working on the electrical system. LOL. i probably shouldn't joke about that. When I installed my amp kit i didn't want to disconect the battery because then I would have to reset the radio clock. Long story short i forgot and grabbed the 0 gauge power cable and grounded cable in the same hand. My 4 year old neice learnt a couple new words that night. Lessons learned - 1. DISCONECT the battery 2. make litle kids cover their ears when i work on the truck
 

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Discussion Starter #12
I am in the middle of replacing the mode actuator. Can someone tell me how the heck you are able to get your hand and a socket up there? I have been working on this for almost 2 hrs and growing more frustrated as time passes. Anyone have any ideas or suggestions? I cannot get the socket to latch on to the bolt.
 

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I have the same problem with a 2006 Envoy Denali.

About a month ago my husbands Envoy Denali's battery went dead. After he jump started it, the AC dashboard blowers wouldn't work anymore. We have meanwhile had a new battery put in, but the dashboard vents don't blow. I found the fuse removal suggestion here and we tried that. Unfortunately it didn't work.

What I would need is some advice how we can fix it by ourselves respectively if it would be a big deal to do that, and of course instructions how to do it :)

I would be grateful for any advice I could get.

:thx
 

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Thank you "The Rodie"

Thank you for your advice. Found the thread. Will forward all the info to my hubby and see if he is willing and able to fix it. :) He already had it at our GMC dealer, but got p...off, when they told him they would charge him $80/h for analyzing and possibly repairing the thing...

Will update you on how it worked. :thx
 

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Dealers LOVE to claim that replacing the actuator requires removing the ENTIRE dashboard and it's a $1000 project. There's a new (to them) special GM tool that makes it a lot faster, and some members here have fabricated something similar. And many others do it without any special tools.

But it can be a frustrating way to save a lot of money. I might recommend getting some of your hubby's favorite beer in stock so you can deliver it at the right intervals, and some earplugs so you don't have to hear ALL the swearing. ;)
 

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had the same problem with mine

I bought the part from the dealer and a friend installed it in less the a half hour. The dealer told me the same thing about taking the dash out but it was able to be replaced with out removeing the dash
 

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Actuator

I pulled the Mode Actuator out and confirmed it moving. It is only moving one way no matter what setting I but it on. It keeps trying to move when it hits the stopping point. Is this bad or is this normal? Can this be fixed other than being replaced?
 

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It's bad. You can try taking the actuator apart and seeing if you have broken teeth or a gear not pressed firmly onto the knurled output shaft, but it's tricky work if you're not experienced in electromechanical repair.
 

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actuator gears fine

The gears are fine from the last time I took it apart. I made sure there was not any broken teeth or anything. Just wants to run only one way and not the other. Thanks you for the help anyways.
 
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