Temp / Mode actuator motors

[Oobray]

Well, all of a sudden (during a snowstorm actually) my HVAC will only blow through the face vents. I researched and found it's most likely the actuator motor. Although, it seems that everyone says that when it fails it defaults to the defrost setting (which is the opposite of mine).

So I got another one at auto zone, pulled the old one, and installed the new one. Problem is, when I change the settings the actuator only moves MAYBE 1/16" so not enough to actually engage the defrost. I removed the actuator and manually manipulated the little half wheel that moves the blend door, and it works fine. So I plugged the actuator in without installing it and cycled through the settings. It doesn't move but fractions of what it looks like it's supposed to be able to. Could it be the switch in the dash isn't sending the proper signals?
Also, when I searched the part number on the old unit on the AutoZone website, it came up with "cross-referenced" and gave me the part number of the replacement. Is it possible that this is the incorrect actuator? Also, while looking at the actuator and cycling the settings I noticed that going from full face, to face/floor the actuator did not move AT ALL. Going from face/floor to full floor it moved slightly. Moving from full floor to floor/defrost it did not move AT ALL. Then going from floor/defrost to full defrost it moved slightly.

Thanks

Sorry, it's a 2002 Yukon XL 2500 8.1

 

[Chiggy]

Have you tried unhooking the battery for about 15 minutes and letting it relearn the positions? When you hook the batter back up DO NOT TOUCH the hvac buttons. Just let it be for a few minutes before you start touching temp, fan, or position.

 

[Oobray]

Have you tried unhooking the battery for about 15 minutes and letting it relearn the positions? When you hook the batter back up DO NOT TOUCH the hvac buttons. Just let it be for a few minutes before you start touching temp, fan, or position.

I tried that after I installed the new one. I tried removing the fuse prior to purchasing the new part, that didn't work either.

 

[Oobray]

Well, turns out it was a faulty actuator motor from Autozone. I replaced it today and now all works perfectly. So, for anyone that comes across this thread when searching here are the part numbers I used. Also, there are a LOT of different part numbers for different applications of chev/GMC depending on what trip level and type of climate control your vehicle has. As you can see in the photos, after you remove the driver's side kick panel, you can visualize the mode actuator motor. So you can manipulate the mode knob and look to see if the actuator is moving. It's it's moving, then obviously that's not your issue, if it's not moving (as in my case) then you have to replace it. Everything I've read says that the device is supposed to fail in the 'defrost' mode; however, mine didn't. It failed in the panel/face mode. Which made the repair difficult because the actuator comes preset to the defrost mode. But, once the actuator motor is removed, you can physically manipulate the actuator assembly ( the black, quarter circle piece of plastic that attaches to the motor and physically moves the cog and wheel on the HVAC). This assembly is easy to manipulate and get lined up with the motor during installation.
I disconnected the battery before installing the motor, that way when I plugged the motor in, it didn't try and do anything funny, and so that way as soon as it was installed all I had to do was plug the battery back in and turn the ignition to 'on' without starting the vehicle. As soon as I did that I could see the actuator moving slightly to "relearn" itself. After about 1-2 minutes, I turned the ignition off, waited a few seconds, turned it back on and switched between modes and watched to confirm that the actuator was moving, and that I could feel air blowing out of where air should be blowing.

So....
Here's the part numbers for my particular vehicle (from Autozone)

Mode blend door actuator Motor: PN#604-113

HVAC Blend Door actuator: PN#604-101 (this controls the blend of hot and cold air, and is located under the glove box on passenger side. It's pretty easy, except for one bolt that required some manipulation. I replaced this because I was already in the dash, and didn't want to have to do it again later).

This is the view basically if you put your head on the brake pedal and looked up toward the center of the dash. I had to remove a portion of the floor vent to get the view, you can see the remaining portion at the bottom left. The little white cog on the upper left is the cog that actuates the floor vents, the little quarter circle with the teeth is what controls the blend door for the panel/defrost vents. When the actuator assembly (the black plastic part connected to the motor which is hard to see in these photos) moves counter clockwise it moves the quarter wheel counter clockwise, thus changing modes. When the assembly pushes far enough, it allows the cog to drop, opening the floor vents. When it turns even further it closes the floor vents and allows only defrost.




This is a view from standing outside the driver's door looking in. Just to give an overview of where I'm at here.





I made a short video showing the motor in action, but I'm having problems with photo bucket at the moment. When I get it uploaded I'll update the post. When I was searching around the net for instructions on this repair I didn't find much specific to my vehicle. There's lots of videos for chevy's but none specific that I found for this trip Yukon, which is basically the same in theory, but slightly different in application than the chevy's. So.... Hopefully if someone else is looking they'll find this post helpful.

 

[RobertWYoung]

Odd-ness

So yesterday I changed my oil, cleaned my AEM air filter, and decided to clean my throttle body.

Now my A/C is full defrost. Hopefully my mode door actuator didn't die.

After work I'm going to turn off the HVA/C, pull the fuse, and disconnect the battery for 15 min.

 

[RobertWYoung]

Looks like the actuator is dead. It always moves past the end and gets stuck. I'm going to order new ones for mode and both front blend (driver and passenger). From what I can see by looking at them they all have the same part number (52402598). Is that not the case? The blend door actuators both have an 07 on them and the Mode door actuator has a DZ.

 

[RobertWYoung]

FYI there is a software update to fix some of this:
http://ww2.justanswer.com/uploads/PE...57_denali1.pdf

I'm going to try that before I replace the actuators.