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Front vents not blowing

99K views 30 replies 15 participants last post by  bgbevan 
#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!
 
#2 ·
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.

 
#11 ·
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
 
#4 ·
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.
 
#5 ·
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:
 
#6 ·
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:
 
#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:
 
#8 ·
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.
 
#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.
 
#13 ·
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
 
#15 ·
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
 
#16 ·
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. ;)
 
#21 ·
actuator gear

Well I took the actuatar apart. The teeth are fine but I did notice the big gear was not pressed on all the way and was out of place. I tried to aline back in place. I did the recalibrating and it found both end points this time. I tried the control head a few minutes later and It was not responding. I tried reposition the gears in the actuator and had not luck. I ended up breaking a gear in the process. I guess I am stuck getting a new actuator. In the mean time I used a wire to pull the vent door down manually to get windsheil and feet for the winter. To reverse, I just shut the air off and let the weight of the door fall back to the front vents. It was a good idea untill the wire popped off. It was worth the shot.
 
#22 ·
Use a shoe lace... lol...

Well I took the actuatar apart. The teeth are fine but I did notice the big gear was not pressed on all the way and was out of place. I tried to aline back in place. I did the recalibrating and it found both end points this time. I tried the control head a few minutes later and It was not responding. I tried reposition the gears in the actuator and had not luck. I ended up breaking a gear in the process. I guess I am stuck getting a new actuator. In the mean time I used a wire to pull the vent door down manually to get windsheil and feet for the winter. To reverse, I just shut the air off and let the weight of the door fall back to the front vents. It was a good idea untill the wire popped off. It was worth the shot.
 
#23 ·
so I replaced my actuator last night, it was kind of a PITA... couldn't get the actuator to align, finally I saw there was a notch, pulled the fuse, and observed as it went through its calibration, shut the power off once it was aligned... moved the vent door gear so the notch on the gear would be parallel with the mounting holes and whala... installed, pulled the fuse once again, and went through its calibration process once more and finally finished... took me about 1.5 hours... granted I spent about 30 minutes trying to take out the floor duct... couldn't get that plastic plug out.. didn't want to yank on it and accidentally breaking it... :) ....:woohoo:
 
#24 · (Edited)
Front Vents not Blowing

I had the same problem after replacing the battery on my 2003 Trailblazer the air would not blow air out the dash vents when on AC it would only blow cold air out the floor vents. I tried the whole routine of pulling the #36 HVAC B fuse and that did not work using the procedure mentioned in another post. Then tried disconnecting the battery cables again and tried to get it to recal with no luck.
I then proceeded to pull the driver side dash apart and was able to get my hand on the Mode actuator and it would not move. I could feel it but could not see it. I then pulled the electrical plug on the operator and moved it manually with a penny in the shaft slot to vent to the dash. This worked fine until I plugged it back in but it returned to vent to the floor. I then unplugged it again and manually moved with the penny to vent out the dash and it works fine now since we need AC here in Florida and not heat, mostly AC but there have been periods of cold here were you need heat.
As I said could only feel actuator and not see since I didn't have a short extention for the socket wrench to pull the bracket that holds part of the center of the dash. If I had of pulled that bracket I believe I could have seen it.
My plan is to order the mode operator and when I have the rest of my tools plan to replace the Mode operator as that appears to be the problem.
All I can say is what a poor design that causes you to replace parts just because after 6-1/2 it was time to replace the battery and now the heater AC parts need to be replaced due only to that??.
 
#25 ·
All I can say is what a poor design that causes you to replace parts just because after 6-1/2 it was time to replace the battery and now the heater AC parts need to be replaced due only to that??.
We agree totally. The design team must have been packed with noob interns without adequate adult supervision, is my analysis. :hissy: Way too many dumb mistakes that an experienced engineer would not have made. :bonk: The GMT360 ends up with a bunch of now-orphan pieces that can be used as examples of how NOT to design a platform. :rolleyes: If only somebody wrote a book and the engineering schools used it as a textbook and the students actually read it and absorbed the lessons. :hopeless
 
#28 ·
rear climate control

hello specially to the roadie i know this thread is old but in a series of attempts to fixing my vent problem i pulled the rear havc fuse and now it wont select between floor and upper vents this on the rear, air does come out but is not cold enough and also the diagram showed from the dashboard has message and it really cant be seen clearly where can i download that? but back to my problem i want to move by hand temperature 'door' and the selector 'door' also so i get cold air from the upper vents for both the drive and passenger side i need to know how to get to those but please no guessing i need to know how its very frustating now that s being 108 degrees here in vegas and on top of that i have a 6 month old girl please this is urgent i need to move by hand both vent and temp door to keep them lock where i want i dont care if i have to disconect them so that they dont move any more and how do i make cold air blow through the back climate control vents thanjks a lot:):thx
 
#29 ·
a/c vents not blowing

I had this problem and thanks to this site, I was able to narrow it down to my mode acutator not working. I fixed it without any new parts. I have an 2006 trailblazer with manual controls. I pulled the lower dash and black panel below off. Just a couple of bolts 7mm I think, two below the steering wheel have plastic covers. You need to pull that rectangular long curvy foot vent on the driver side under the dash out they way. It's held in by one plastic pin on the door side that just pops out and in, so pull it down from the door side and don't be afraid. Then when laying down under there you can see 3 black acutators. The one by the firewall is for the window defroster and floor vents. The one next to that is for the main vents. Not sure what the one close to the steering wheel is for. Pull the HVAC fuse under the rear passenger seat out for 30 secs. and put in back in. Put the key in the ignition, but DON'T TURN IT YET. Lay back down and then turn the key. You will see the silver slotted gears on the actuators reset. My main vent was not moving, problem found. I took it out, with some patience and a 7/32 socket on a small screw driver, it also has a connecter the you just press and pull out. Don't drop the screws. It has a white gear attached to it that can be pulled out. Remember the postions. Then after going to buy one, I got the wrong one and had to return it. The only store around with it in stock was NAPA and they were also the only ones that closed at 5:00. So I thought I would have to wait a day, and then decided to look inside the actuator. While closed I could not turn the gear. I opened it and saw all the gears and the motor. I pulled the motor out and the gears could all turn, bad motor right, wrong. I put the motor back in and pressed all the gears. the small green one attached to the mother board went down and was not connecting with the big gear. I raised it a little and decided to give it a try. Hooked it up with out putting it back in, did the reset again and it moved but then stopped. I disconnected it and opened it again. That same gear was down again. This time I put it up as high as it could go, put the cover on gently and flipped it upside down, then snapped it in place, so I wouldn't vibrate the gear down. I put the white gear back in and had to hook it up and let it run a little, then stop because it was all the was to one side and wouldn't line up, screwed it in and was back in business. Everything worked. This may not work for everyone, some have said their gears were broken inside. Mine were fine, just the one with the motherboard slipped.
 
#30 ·
Ac not working at all

I had paid someone to change out my factory stereo in my 07 chevrolet trailblazer. When i left i tried using my a/c and nothing was blowing out of the vents at the top. I've tried getting a new a/c control module, replaced it and it still didn't work at all. I disconnected the battery along with the hvac fuses for 30 seconds. Put the fuses back in and started my car and still no luck at all. I then waited for about 2 mins to let it recalibrate on its own and still no luck. I cant seem to find out what the issue? Anybody know what i can do to get some a/c or heat to work in my top vents. My bottom vents work just fine for heat but no a/c. My rear doesnt work at all either. What other things could i try to get my a/c blowing back to normal?
 
#31 · (Edited)
Dash Vents Won't Blow Hot or Cold

My car is a 2003 Envoy with around 140K miles

You have probably read a lot of other posts by the time you get to this one, so I won’t go into a lot of detail that’s already been hashed over. My A/C wouldn’t blow through the dash vents, no matter where the mode selector switch was set. (The mode switch is the one that selects which vents heat and air blow out of.) The vents are controlled by actuators which are just small motors that open and close various doors that determine where the air goes. Like many of the posts, my problem occurred when I reconnected the battery after storing the car for 6 months.

From all the previous posts, I figured the mode door actuator had failed. You can try the recalibration process included at the end of this blog and it might correct the issue. I tried it numerous times but although the actuator moved, it would only go one direction and then stay there. An optional double check would be to take the car to a GMC dealer and have them run a diagnostic check. My diagnosis showed code “B0263, mode door actuator stuck”. The cost was $65 but I knew for sure I had the correct diagnosis. Quote for the dealer to make the repairs, $528.

I pulled the two dash panels on the driver’s side under the steering column, the silver crash bracket under the column, and the plastic vent that routes air over to the driver’s side. Tip: Be careful when removing the plastic vent push screw because the bracket is fragile and easily broken. You need a 5.5mm, 7mm, and 10mm sockets to remove this stuff. Looking up under the dash above the gas pedal, you will see two black actuators. The mode door actuator is the one farthest from the firewall. Ordered the actuator from Amazon, AC/Delco Part #15-73596, GM part #89018675, for $43. Removed the failed actuator with a 5.5mm socket…..two screws hold it in. A little tricky getting at the back screw. If you want to test the system to make sure air comes out of the dash vents, reach up and turn the actuator gear fully CW. When you are ready to install the new actuator, turn the gear on the door(not on the actuator) by hand to about the mid-point in it’s travel. The white actuator arm has a notch that mates with the door gear so there is only one way it will fit. You may have to do a little back and forth to get the notch and gear to align. Then hold the actuator in place while you get the screws started and tightened down.

Now for the big test. Lots of previous posts on making sure everything is calibrated. This calibration procedure worked for me: Ignition off, A/C off, blower switch off, remove fuse 36(or disconnect the battery), wait 2 mins, insert fuse 36(or reconnect battery), ignition two clicks to run but don’t start, wait 2 mins, start car, turn on A/C & blower, test mode switch. Everything should work now.
 

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