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2005 STS (V8 AWD)
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Discussion Starter #1
Longtime reader / first-time poster here, begging for a bit of help. Here's my issue:

Yesterday, I changed the battery in my STS. I didn't take any steps to preserve the memory (lesson learned).

Immediately afterward, I took the car in for inspection. It failed because the defroster wasn't working. I was very surprised, as I drive this car every day and hadn't noticed this issue. So I feel about 90% certain that it started when I changed my battery. When I got home, I played around with it some more and discovered that the vent selector control simply wasn't working at all. (i.e., no matter what it's selected to, the car blows air out of the dash and bottom vents).

So in short: Does anyone have any thoughts on how changing a battery could cause the vent selector control to stop working?

Here's what I've tried already:

(1) I thought I might have blown a fuse, but I opened up the fuse box and pulled the blower and CCP fuses, but they looked fine.

(2) I thought (and still suspect) that unplugging the battery may have done something to the computer's HVAC software, so I tried to reset it by unplugging the battery a few more times, but had no luck.

Any thoughts would be greatly appreciated! It's a bit tough to find an honest mechanic where I live, so I'm trying to narrow things down as much as possible on my own first. Thanks in advance!

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Update:

Here's someone describing the same issue with their 2003 Chevy Silverado: http://smith-wessonforum.com/lounge/265214-replaced-battery-ac-vents-not-working.html

The fix proposed on that thread doesn't seem to work for my Caddy, but it does lead me to believe that the issue is with the computer.
 

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2005 STS V8
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215 Posts
I'd reach up and touch your mode actuator (top actuator on passenger side) while someone is switching the vent positions. If you can feel it trying to move and nothing is happening its toast. I just finished replacing mine and it involves removing the entire dash/dash carrier..
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Did you touch any controls after reconnecting the battery within the first couple of minutes? During this time the HVAC module is automatically attempting to do a door position learn function and you're not supposed to touch anything.

When you disconnected the battery, did you touch the cables together for a few seconds? If not, you may want to try this.
 

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2005 STS (V8 AWD)
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Discussion Starter #4
ddalder: thanks much for your reply. I've tried several methods of resetting the computer by disconnecting the battery (including touching the cables together and also not touching the controls after reconnecting), but unfortunately haven't had any luck.

nwjones18: thanks also for your reply! When you say "reach up and touch" the mode actuator, is this something that's possible to do without removing the dash? (i.e., I know the whole dash needs to come off for a replacement job, but is there a simple way to reach up and touch it for testing purposes?)I hope mine isn't toasted as well, but perhaps it is.

Still holding out hope for a simple fix . . . any other brainstorming thoughts are much appreciated. Thanks!
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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If this was my car the next step would be to have it scanned for codes. There are also some tests that can be completed with a Tech2 but you will either need to know someone that has one or go to a dealer.

Out of curiosity, what order did you reconnect you battery cables in?
 

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2005 STS (V8 AWD)
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Discussion Starter #6
Thanks ddalder -- I agree that that'll have to be the next step. I don't have a code reader, but my local auto part store will often let me borrow theirs.

As for the battery, I reconnected red (positive) first, then black, which has always been my standard practice.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Their code reader may or may not be able to pull codes from the HVAC but it's worth a try. As for the cables, I ask because I've been reading information from GM recently that stresses the importance of disconnecting the negative first and reconnecting the negative last. They have been experiencing an increase in modules being damaged when this order isn't followed.

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I can say that my experience with other vehicles has been when a fault exists, the HVAC will always adjust to the defrost position. I understand this may be a safety requirement so that the windshield can be kept clear. I haven't actually read this anywhere myself but I also haven't looked. This 'may' suggest there's a problem the system is sensing.
 

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2006 STS V8 AWD, '95 Ford Ranger
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28,963 Posts
Auto parts store code readers don't read anything but generic engine codes. You need to go to a dealer or a high end independent shop.
 

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2005 STS (V8 AWD)
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Discussion Starter #9
Thanks again, ddalder and dkozloski -- I'll see what I can get done this weekend in terms of pulling the codes. My local dealership's service center is a last-resort option for me (have had a few too many unsatisfactory experiences with them), but perhaps I can find a good independent shop.

As always, any additional thoughts are much appreciated. (In particular, if anyone knows of a way to test the mode actuator without pulling the dash, I'd like to give that a try.)
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Without a Tech2 I'm unaware of any further testing you can do that's relatively easy. You can try having it scanned at a parts store. We have a few around here that do have better scan tools and can pull some non-powertrain codes. I haven't seen any yet though that have been able to pull ABS or SIR data. I think it's hit and miss what you may find without a dealer or other designated service facility.
 

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2005 STS V8
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You can literally touch it and if you feel it 'shivering' trying to change positions and if it doesn't then it is bad.... just have to lay in the passenger floorboard and look at it.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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You can literally touch it and if you feel it 'shivering' trying to change positions and if it doesn't then it is bad.... just have to lay in the passenger floorboard and look at it.
This vehicle has multiple actuators and the mode actuator that switches between defrost and the other vents is actually on the driver's side of the vehicle and not easy to access. I think you've got this confused with another one.

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Just to recap, the right side of the HVAC air box has the Right Temperature Actuator and the Recirc Actuator. The left side has the Mode actuator and the Left Temperature Actuator. There is also an Auxiliary Actuator in the center console.
 

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2005 STS V8
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This vehicle has multiple actuators and the mode actuator that switches between defrost and the other vents is actually on the driver's side of the vehicle and not easy to access. I think you've got this confused with another one.

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Just to recap, the right side of the HVAC air box has the Right Temperature Actuator and the Recirc Actuator. The left side has the Mode actuator and the Left Temperature Actuator. There is also an Auxiliary Actuator in the center console.
Sorry I think you are a little bit confused as to the locations of the modules. I just finished replacing all of them and know where they are. Top one on the drivers side is the drivers temp actuator. Bottom on drivers side controls mode for the center console. Top one on the passenger side towards the center of the vehicle is the mode actuator and controls defrost/vent position. Bottom controls passenger side temperature. The recirculation motor is located on the blower motor housing on the passenger side.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Did you do the work yourself or did someone do it for you and this is what they said? I've had mine completely apart and watched as it cycled mode settings. The mode actuator has a large white wheel attached to it. I've had mine apart and I'm quite certain as to which side it's on. Clearly there is conflicting information in the service manual because this is a picture of Step #2 "Disconnect the mode actuator electrical connector."

You will notice that the white tube used to draw ambient air back from the dash is noted in this diagram and it only exists on the driver's side. I saw the image that you posted in the FSM, but have a look through the service procedure for replacing mode actuator because that information conflicts with your post.



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Regardless, what you're suggesting about simply grabbing the actuator and checking for resistance/vibration is not a definitive test to determine if it is working or not. It needs to be cycled through full travel with sensor readings being monitored. The only way to accomplish this is with a Tech2.
 

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We are going to have to agree to disagree on the subject. I did all of the work myself and had the entire dash carrier out of the vehicle. I replaced 4 of the HVAC actuators including the mode actuator. I agree that touching it is not a definitive test, but if it is visibly 'quivering' or stuck its a pretty sure bet that the motor is shot. I was wrong in saying that the lower actuator on the drivers side is the mode actuator for the console it is in fact the temperature actuator for the console. Lower one in your picture. The Mode actuator for the console is in the console itself.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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I certainly see where you're coming from. Unfortunately when I had mine apart, I didn't take the usual 500 pics. Any of the ones I have aren't clear enough and at the right angle. It was some time ago when I had my dash out so perhaps I'm backwards on this. Either way, there is definitely some conflicting info in GM's service documentation which is what I was relying on to refresh my memory.
 

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2005 STS V-8 1SF Magneride HUD/ACC, 2008 Escalade ESV 1SZ Y91 Luxury Edition
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...3 years later, Did you get it fixed?
Before resurrecting old dead threads, check the poster's profile. He hasn't been on the forum since just a month after he joined in 2015
 
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