2006 Chevy Trailblazer EXT LT 5.3L...NEED HELP...Rear HVAC issues

HOOKER/LIFE

Original poster
Member
May 12, 2021
2
30078
I am at witz end. I bought this vehicle back in August of 2020. I have replaced the rear hvac blower control resistor, both blender door actuators to control hot/cold and vent position. Ive replaced the cabin temp sensor that's located in the driver's side front pillar. I have also replaced both the front digital hvac control module on the dash, as well as the digital hvac/radio controller that sits inside the center console for the backseat to control music/ac. I cannot to this day get the rear hvac blender door to change from hot or to cold, it just blows warm, and also I cannot get the rear hvac vents to switch to the roof or floor, it's stuck on floor. I've done multiple rounds of the pull such n such fuse for X amount of time with vehicle off. And then replace fuse or fuses after X amount of time and then run the key to on position and wait X amount of time to calibrate actuators. Can some one please help me. 🙏
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
When you replaced the HVAC control, was it from another EXT of the same year? Or it may need to be programmed for it.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
When you pull the battery terminals off, wait the 5 minutes, and reconnect, are you checking the HVAC motors at the rear to see if they calibrate? If they dont calibrate, than thats the place to start checking for problems. I remember that there also needs to be a certain position for the front and rear controls to be in, for them to calibrate correctly.

And its a very specific amount of time.. I know I just did a write up on this somewhere in the forum... Have to see if I can find it.

Edit: Wow I found it!

So this process here is after you have disconnected the battery for 5 minutes, then reconnecting the battery. The problem is, I cant find the tech write up thats says what the AC front and rear controls needs to be in.. I could guess, but it would just be a guess.

 
Last edited:

HOOKER/LIFE

Original poster
Member
May 12, 2021
2
30078
When you replaced the HVAC control, was it from another EXT of the same year? Or it may need to be programmed for it.
I bought brand new and disconnected the battery before removal of old unit to install new unit. I followed all the guidelines to program it but it never gave me the option on the control until it was already done ready to go. I did how ever pull all hvac fuses with ignition off and wait and plug them back in the turn vehicle to on position. I can hear 1 actuator in the rear hvac unit cycle and I've wait 30mins with key in on positions. Still no luck. I just ordered acdelco factory actuators in hope its something stupid with the cheap ones I bought before hand
 

Mektek

Member
May 2, 2017
656
FL
I think you need to have a new HVAC control flashed with a tech2 to your specific year and model. The replacement actuators are probably not the source of the problem.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Agreed. It has to be programmed for your specific vehicle. It needs to be programmed by either a dealer or a shop capable of doing this. That's why we usually recommend just replacing it with a used one from the same vehicle.
 

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