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post #1 of 4 Old 10-04-2013, 02:05 PM Thread Starter
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AZC experts please read :)

Sorry for yet another AZC thread. I have scoured the forums with no success. I am trying to fix a blend door problem and am stumped. I will describe what I have done and what my symptoms were/are, hopefully somebody has seen this before, and I apologize in advance for the lengthy post.

I have a 2004 Limited with the AZC. Last winter, I discovered I had the dreaded broken blend door problem when I began troubleshooting no heat on the passenger side. I pulled the dash and the HVAC unit and replaced the blend doors and the recirc door with Dorman replacements. The recirc door didn't need replacement, but since I was in there I decided to change it out. The blend doors were broken, the hinge was cracked preventing the passenger door from moving with the actuator, resulting in the door remaining in full cold position.

I reassembled everything, had the AC serviced, and everything seemed fine; until the first 100+ day of summer. The passenger side didn't seem to blow quite as cold as the driver side. After troubleshooting, and running the AZC disagnostic, I was getting codes 54 and 56 for L/R door travel too large. I also noticed the doors seemed noisier than usual.

So, I pulled the dash and HVAC unit again. bench tested actuators and noticed that the actuators continued to turn even after the door reached full travel. The doors were stopping, but the collars of the actuator (that connect over plastic "pin" on the door hinge) were deforming thus not allowing for enough increase in resistance to send a 'shutoff' signal to the controller. I replaced the actuators and reassembled everything.

Now the actuators stop when the door reaches full travel after approximately a 1 sec delay (seems like an unusual amount of force required to send the 'shutoff' signal to the control module). From reading other posts I am assuming this is normal.

After running the AZC auto calibration, I still get codes 54 and 56. When I clear them, everything seems normal (no codes) until I select Lo or Hi in order to test the extremes of door travel. Anytime I reach an extreme the system records a code for door travel too large.

I bought a control panel off ebay, but think it is incompatible. When I swapped it in, I still got door travel too large for the right (22), but the left door wasn't controlled at all (code 15). Suspect it is a control panel from 2002 or earlier. The date stamp was 12-16-05, part number P55116709AF so I thought it was an upgraded part, but I now think this is not the case.

So, should I try ANOTHER control panel, or is there some other line of troubleshooting I have not considered?

Sorry again for the long post, but any insight is greatly appreciated!


p3vinny is offline  
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post #2 of 4 Old 10-04-2013, 11:09 PM
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What brand did you go with for your actuators? I vaguely remember hearing about poor quality replacement actuators that didn't have the torque capability to deliver the required amp draw that the AZC system saw as a end point. It could be worth picking up another one from an auto parts store and swapping it out for the drivers side and see if it makes any difference. Provided the doors and drive connectors are in properly good condition (seeing dormans stuff firsthand, it seems unlikely they would be damaged) and the doors are in fact stopping at full travel, it has to be either faulty actuators or the AZC headunit. I'm not sure about the compatibility between years on the head unit, but the fact that you got an over travel code on two head units would say to me that that isn't the best area to pursue.
Schlotzky is offline  
post #3 of 4 Old 10-05-2013, 01:27 AM Thread Starter
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Thanks for the reply! I used Dorman replacement actuators. They are definitely applying enough torque, and the doors are still working as they should.
I did try swapping out the actuator from the recirc door as well as swapping the original actuators front to back, but the result was the same. Based on observing the same thing with multiple actuators I'm leaning towards a faulty control module.

Besides not liking it when a system is not working properly, I am also concerned that the continued 'overtravel' of the actuators could damage the blend doors. I've ordered another control panel and will try to swap it for troubleshooting. I'll update this thread if I figure something out!

Thanks again for the reply!

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post #4 of 4 Old 10-05-2013, 12:39 PM
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Sounds like you're on the right track, then. I can't think of many other areas that would have this effect, other than perhaps an electrical issue. It's never a bad idea to clean up your battery terminals and check for loose or corroded grounds inside and in the engine bay, but it would seem like a new head unit is still the next logical place to troubleshoot.

Good luck!
Schlotzky is offline  

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