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chevy trailblazer_lt_ext
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I thought I fixed it!

Well, after I fixed this issue Saturday morning on the 05 TB, everything seemed to fine. the family didn't drive the vehicle much on Saturday, Sunday I didn't drive it at all, Wife used it around town and such, still no problems. It was kinda "chilly" here on Sunday, no not much need for air flow. Anyway, now it's Monday morning and AIR will not blow out of the bottom. Stuck on the front vents now and on top. UGH!!

I guess disconnecting the battery to reset the actuator is worth a try.

Any ideas please?

Thanks
Taz
 

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2004 chevy trailblazer_lt
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4 Posts
This is my first post and I wanted to say thank God for this site!!! Old story here, I changed the battery and of course the air quit blowing through the dash vents and the passenger side defroster and floor vents were blowing hot. I read this entire thread several times over and decided to "fix" the problems. I did not replace the mode actuator or the passenger temp actuator. I simply unpluged each actuator and turned the metal part of the gear drive on the mode actuator until I got air through the driver side dash vents. I then turned the passenger temp. actuator until the air blew cold through the passenger side dash vents and the rear air. The reason I did not replace these are my finances are extremely tight (I have two daughters in college and two more in high school). I guess when it gets cold I will have to deal with the passenger temp. actuator (I sure don't look forward to replacing that as there is very little room to work with).

This was on my daughter's 2004 Trailblazer.
 

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2004 chevy trailblazer_lt_ext
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3 Posts
for EXT

I read through this and other links when I found my air was only coming out the defrosters and the floor. I tried pulling the fuses for the HVAC and letting the system reset with the key in the "on" position (at night with the doors closed you could hear them one at a time resetting) was hopeful that would solve it, but problem remained.

I was ready to order the part, but finances are tight. The next day it got a little warm here and I decided to test what I had while out running errands. The EXT's have the rear air controls, which I turned up all the way, and within about 3 minutes I was freezing.

I'm gonna roll with it until I have the time and money to mess with replacing the actuators or the problem gets worse and I start roasting in the summer heat.

Just something for those of you that are noticing the air won't come through the vents, but may get the impression that you have no air at all.

*SOME folks are having an issue where the air won't come out of the dash vents AND won't blow cold.

my:m2:

 

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2004 buick rainier
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201 Posts
Difference in temperature between driver's side and passenger side does not always mean a bad actuator or bad temp sensor!

I took my Rainier into the shop this week for this problem. The cause was that it was low on refrigerant. The A/C now blows very cold on both sides. The mechanic said I most likely have a leak but its very, very slow and he couldn't find it.

How much does a new A/C compressor cost?
 

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2004 gmc envoy_slt
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36 Posts
In the middle of swapping the mode door actuator. I ordered a new one and trying to put it in. For some reason after i power up the mode door will go to one side to its limit and just stop. It will not respond after that. I will have to remove the cover to unjam the gears and try again. I have done the battery thing. Im going to try the fuses now under the rear seat. I can manual move the door and have it moved to the front vents which mean the actuator is at 1 oclock position I believe but still no help. If any one has any ideas I would appreciate it if you can get to me fast. I have been working this thing for 4 hours now. Thanks.
 

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2004 gmc
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26,181 Posts
Is it too late to match the position of the new one to where the old one was when you took it off? If you take the cover off and work on the gears, you have to very, very cautious around the blue sensor. It's a potentiometer, like a volume control, but it doesn't have any stops. It can spin around and around. If it's in the wrong position relative to the final output gear, it can spin around and then maximum CW and maximum CCW gear positions aren't accurately reported back to the control module. And then the power-up calibration process fails, and as you see, then the control module abandons talking to that actuator until you pull the fuse. That forces a new calibration cycle when you turn on the ignition again.

It's possible to lose position feedback altogether. I did that accidentally while fixing mine. All I needed to do was press the final gear back further on its knurled shaft so it didn't slip, but I messed up the potentiometer relationship when I unstacked the gear train, and it took me an hour of figuring it out and reassembling it to make it work. And I'm an electrical engineer and understand how it was supposed to work. :eek:
 

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2004 gmc envoy_slt
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36 Posts
Yea I finally figured out the little blue gear about half hour ago. I think I finally have it doing it cal and everything, just have to figure out the right position to put it back in. I was using the position of the old one but with my old one the gears in side exploded so the shaft wasnt turning when I was changing modes when it first happened to figure out why I it wasnt changing. So yea position is lost. But like I said I think I may have it but when I went to try it, my battery died, So I have to wait till the wife gets home so I can jump it. Im in the process of putting on liftgate struts as I type and change the EVAP solanoid.

Will report back once I get a jump and see how it acts.
 

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2004 gmc envoy_slt
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36 Posts
Is it too late to match the position of the new one to where the old one was when you took it off? If you take the cover off and work on the gears, you have to very, very cautious around the blue sensor. It's a potentiometer, like a volume control, but it doesn't have any stops. It can spin around and around. If it's in the wrong position relative to the final output gear, it can spin around and then maximum CW and maximum CCW gear positions aren't accurately reported back to the control module. And then the power-up calibration process fails, and as you see, then the control module abandons talking to that actuator until you pull the fuse. That forces a new calibration cycle when you turn on the ignition again.

It's possible to lose position feedback altogether. I did that accidentally while fixing mine. All I needed to do was press the final gear back further on its knurled shaft so it didn't slip, but I messed up the potentiometer relationship when I unstacked the gear train, and it took me an hour of figuring it out and reassembling it to make it work. And I'm an electrical engineer and understand how it was supposed to work. :eek:
Yep roadie that is exactly what is going on. I worked on it for another hour or so and still couldnt get it. I will have to tackle this tomorrow and see if I can figure it out. I had it once but when i would switch vents to the floor it wouldnt completely turn off the upper vents. So i messed around a bit with it some more and lost it. This is officially a pain now. Oh and so far after about 10 start ups the evap vent solenoid hasnt cleared my SES light, oh yay! :mad::confused:
 

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2003 chevy trailblazer_lt_ext
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6 Posts
put it in

ok, I bought the new part, installed it and now it seems as if the air comes out up top but when switched over to heat on the floor nothing is coming out. Can I adjust this with a large flathead on the backside of the where the gear goes ?..........................Jeff:bonk:
 

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2004 chevy trailblazer_ls_ext
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815 Posts
ok, I bought the new part, installed it and now it seems as if the air comes out up top but when switched over to heat on the floor nothing is coming out. Can I adjust this with a large flathead on the backside of the where the gear goes ?..........................Jeff:bonk:


no you will need to take it out and visually watch as the gear adjust, once it aligns with the notch, quickly turn the ignition to off...
 

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2004 chevy trailblazer_lt
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100 Posts
Okay I am sure this has been posted a million times but I read through quite a bit and haven't found my answer.
I disconnected the battery like most others on here and now air only comes from the floor and defrost. I wouldnt say that I hear clicking, more like a contant whine while the motor tries to move and nothing happens. Do you think I have a bad one? I tried recalibrating a couple of times but nothing happened.

My question is that if I get a new one how do I make sure I dont break that one too? I understand that I have to put the new one in at the same position the old ones came out. Do it just plug the new one in without installing it, wait for the calibration to do its thing and change the vent mode until it lines up with the old one? What vent mode would that be?
 

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2004 chevy trailblazer_lt
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100 Posts
Quick update on my progress. I got the old actuator out and took a look at it. Gears look perfectly fine. I cant seem to get the actuator to calibrate thought. It will move to the vent position if I pull the fuse while the ignition is on. I am not sure what that means but at least I know that the gears are all working and it moves. However, if I try the calibrate procedure it doesent want to move, It moves all the way to where the gear fan is inwards and stops.
Any tips or advice?
 

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2006 gmc envoy_slt_xl
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5 Posts
the P/N I used was 89018675 and I got it from www.parts4chevys.com for $46.33 which was alot cheaper than the dealership.
GMPartsdirect.com GM LIST: $66.12 OUR PRICE: $34.38
How do I get the "our price"? I need to get one. Thanks and great help on this site...you guys have saved me more than once. Usually the same known problems and at the estimaed milage right on time. I gotta do the damn sending unit next....Love our Envoy though....
 

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2004 chevy trailblazer_lt
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100 Posts
I cant seem to get the new actuator lined up to the hvac gear. The hvac gear sort of flops down with gravity to the top vent mode. Where does the gear need to be on the actuator to match this? Any tips?
 

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2006 gmc envoy_slt_xl
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5 Posts
What I did last night to fix this was to plug the actuator in while it was not installed and set it to dash vent since that seemed to be the location the door was in manually (due to gravity). It went right in. I spent 2 hrs cussing like a sailer because of this. So now it is in but the dash vent wont totally shut off. I tried the disconnect wiring/battery/etc and nothing changes. Another 2 hours go by and take it out 4 more times trying differieng way s of doing it. Put it all back together madder than hell.

ANYONE PLEASE HELP!!! I dont want to take it to the stealership after spending this much time on it. I hated to do teh battery disconnect to reset this since that is what caused this issue in the first place. PLEASE PLEASE PLEASE help...
 

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2004 chevy trailblazer_lt
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100 Posts
What I did last night to fix this was to plug the actuator in while it was not installed and set it to dash vent since that seemed to be the location the door was in manually (due to gravity). It went right in. I spent 2 hrs cussing like a sailer because of this. So now it is in but the dash vent wont totally shut off. I tried the disconnect wiring/battery/etc and nothing changes. Another 2 hours go by and take it out 4 more times trying differieng way s of doing it. Put it all back together madder than hell.

ANYONE PLEASE HELP!!! I dont want to take it to the stealership after spending this much time on it. I hated to do teh battery disconnect to reset this since that is what caused this issue in the first place. PLEASE PLEASE PLEASE help...
Here is what I found out from a guy I know at the dealer. Mine is working perfect now. If you buy a new actuator you don't need to move the gears at all. It should line up exactly the way it should. Just make sure your HVAC gear in the vehicle is fully clockwise (blowing out the vents).
I made the same mistake you did and tried calibrating while the actuator was not installed. You cannot do that. But if you did, you will need to move the gears back to the correct position. To do this you can take the cover off the actuator as shown below.

Make sure you don't let the large gear and the small blue gear skip any teeth while messing with it. You might want to make a mark just in case.
Take the medium sized grey gear out as shown.

Then you can spin the large grey and blue gear to where they need to be. Line the blue gear up exactly like it is shown below.

considering you haven't skipped any teeth in the gears from the previous calibration attempts, your actuator wing should be in this position.(note the metal tab on the metal shaft and the small groove in the plastic)

Once everything is lined up exactly like that you should be able to put it back together and install the actuator. Pull your HVAC B fuse for a minute and put it back in. Turn the key to on but don't start the car. Don't touch your HVAC controls. You should be able to see the metal part on the back of the actuator move from one side to the other. Then it will be calibrated.
 

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2006 gmc envoy_slt_xl
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Once everything is lined up exactly like that you should be able to put it back together and install the actuator. Pull your HVAC B fuse for a minute and put it back in. Turn the key to on but don't start the car. Don't touch your HVAC controls. You should be able to see the metal part on the back of the actuator move from one side to the other. Then it will be calibrated.

Not to doubt you, but it looks like that's where it was when I started and it would not seat down on the center shaft support, bolt hole supports and the pin locator. It rocked side to side (bolt hole to bolt hole) like it was not setting down. I would hate to go through all this and be right back where I was. Do you truely think this will do it?
 

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2004 chevy trailblazer_lt
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100 Posts
Not to doubt you, but it looks like that's where it was when I started and it would not seat down on the center shaft support, bolt hole supports and the pin locator. It rocked side to side (bolt hole to bolt hole) like it was not setting down. I would hate to go through all this and be right back where I was. Do you truely think this will do it?
That is what worked for me. Just make sure the gear for the fan door gear in the vehicle is turned all the way clockwise so that the air blows out the vents. Without the actuator in it usually goes to that postion from gravity anyways. I know it is a pain in the rear, trust me, I am still sore from the crazy positions I had to get in to get at the thing.
 

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2003 gmc envoy_slt_xl
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14 Posts
Rear HVAC Actuator Won't Come Off Shaft

I couldn't get my rear HVAC actuator to come off the shaft. I wasn't sure if there was a release mechanism on it, and I was afraid that I was going to break the shaft if I pulled too hard. I finally sprayed some WD-40 on the shaft, and that did the trick. It looks like it is fixed now.

Mark
 
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