Auto Climate Control Blows Hot On AC in Rear

Discussion in 'Tech Info' started by Wes 03 Yukon, Jun 5, 2017.

Car Parts
  1. Wes 03 Yukon

    Wes 03 Yukon TYF Newbie

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    For about a month now, my wife has been complaining that the rear AC in her 2003 Yukon Denali has been blowing hot air only. This wasn't a huge problem until the summer temps started creeping up here in Colorado. I finally knuckled down and did some investigating today. Long story short, the blend door itself is busted and was stuck in the heating direction.
    Now for the long story. This could also serve as a general rear climate conditioning overview as I tried to get some pretty informative pictures along the way.
    This is where the project begins:
    Remove the upper rear pillar trim, the black screw in anchor, the grey plastic trim clip, and the rear floor trim. This will allow removal of the quarter panel trim.
    There are two small tabs on the 12V outlet...
    ... and one small relief in the trim panel.

    Slide one tab out, then rotate the outlet until the other one slides out. After removing the trim it looks like this:

    After some online reading I decided to begin troubleshooting at the blend door actuator.

    I removed the actuator and took the cover off to inspect the internals.

    Everything looked fine so I reconnected the wire plug and turned on the ignition. The actuator came to life and appeared to be working normally. Slightly dismayed, I started to put the actuator back on, but something didn't feel right. The blend door arm that is driven by the actuator looked like this when I first pulled the actuator:

    And after attempting to reinstall the actuator, the arm looked like this:
    Removal of the heater core by removing the plastic retaining shield and sliding it out,

    allowed me access to retrieve the broken chunk of blend door.

    I could not find any foreign objects that blocked the door, so my suspicion is that the door somehow bound up and the activator just kept turning. In my attempts to find a solution I also removed the blower motor hoping for better access.

    However, the air discharges out the back of the housing, so I couldn't reach the blend door, but it did let me squeeze my hand behind the unit to find the linkage that attaches the two doors together.
    On a side note, if you attempt to remove the outer top housing you simply remove all the metal clips, but there are two hidden screws just to the left of the blower that attach the outer to the inner housing.

    That's as far into the project as I went for the time being. I slid a piece of Tek Foil insulation in below the heater core and closed the blend doors. I put the insulation in just in case the doors fall back open while the truck is being driven. What really matters is that I turned on the AC and it blew out ice cold. I consider that a short term win until I can find a blend door for replacement. Feel free to hit me up with any questions or comments.
     
    Sam Harris likes this.
  2. cmc76

    cmc76 Full Access Member

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    i have a similar issue, but its telling me i dont have permission to see the pictures you posted.
     
  3. Wes 03 Yukon

    Wes 03 Yukon TYF Newbie

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    This was my first post on this site, but I think I figured it out. Try reloading the post now that I shared my photo album publicly. Let me know if it works or if you have any questions, I'm happy to help.
     
  4. Justinj360

    Justinj360 Supporting Member

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    Is there one or two blend door actuators for the rear? Just getting started with diagnosing my own rear HVAC issue.
     
  5. oldchev

    oldchev Member

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    All good information, especially when including pictures. That helps the DIY Guy.
    I have gone here before replacing the rear door blend actuator having heard a tick, tick, tick, sound and warm air during a/c function. Replacing the actuator fixed the problem for three years. Now I hear that ominous sound again with the same problem. Guess what?

    Last time after removing the actuator I could easily move the blend door shaft with my fingers so not the same issue as this post. I did not disassemble the old actuator to look inside but my understanding is the plastic gears (probably the jack screw) is no longer fully engaging. It maybe the motor has reached its throw limit? Maybe I could move the gear position and reset it? I am pretty sure from what I have heard, once that actuator ticks (gear slip) its toast. I don't know.

    I am going to replace the actuator again. Being that I used the correct number AC Delco unit and it failed I may go with an off brand generic unit this time. I have replaced all the front actuators in separate events also. It seems these actuators are an Achilles heel on this truck platform A/C units.
     
  6. oldchev

    oldchev Member

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    I expected a actuator issue but I found the same broken shaft on the blend door. This door operates the second door along side it's via a linkage. I epoxied mine back together because the break fit tight. 20190612_155949.jpg 20190612_155959.jpg 20190612_160607.jpg
    Before and after this is the shaft and door (one piece). You have to take the upper two case halves out and split them (clips hold together) to facilitate removing the shaft for repair. You might be able to epoxy without removing the halves but it is awkward.

    20190612_160909.jpg 20190612_172045.jpg

    I saw a video online about this plus other pictures and the other ones shown broke nearly identical how mine broke.
    The video user actually bought a new GM case with actuator doors. These are available online from GM parts and the fav online store. Part number is GM 88891577. Depending on where and how you buy expect $90-$110 (or more) for this which seems rather reasonable for what it is.

    Keep track of location of every screw and clip because there are many. I have 3 left over : ( … I also have a brand new blend door actuator I didn't really need. Perhaps a little more research would have saved that purchase however I have a spare now. Otherwise I could have fixed this for time plus epoxy. I used a couple pry tools to remove the trim parts plus a 7mm socket and extension and a 7mm wrench plus a bright flashlight. Small hands are a plus.
     
  7. oldchev

    oldchev Member

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    Just an update to the previous post...the epoxied shaft did not last more than two days. I bought the new upper case half with included blend doors as the fix. This installation took much less time having just had it apart a couple days prior. All good now.
     

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