AC / Htr

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ID Status Date Year Make Model Transmission Type A/C Controls Public/Private
#15557 Closed 2002 Chev Tahoe public

I have a 2002 Tahoe LT with auto htr/ac controls. I replaced the battery and now the controls are stuck on defrost. The temp changes from hot to cold. I have had the battery disconnect several times and always done the same thing which is connect the battery, turn the ignition on and let the controls recalibrate. This time it won’t work. I tried several times. I can here the actuators moving. I can’t find this technique on the net any more. I could be missing a step or doing it wrong. I tried removing the fuses, but that didn’t work either. I also subscribe to Alldata but could not find it in there either. Any words of wisdom. The system has been working flawlessly. All I did was change the battery……Thanks dj
Sparky

I would recommend trying the following recalibration procedure. If it does not help you will likely need to replace the mode actuator.

Actuator Recalibration

The HVAC control module will relearn the actuator limits whenever power is disconnected and re-connected to the module.

Use the following steps to perform the calibration update:

    1. Turn OFF the ignition.
    2. Remove the battery positive voltage circuit fuse (Radio in underhood fuse box)  of the HVAC Control Module.

Important:  The scan tool must be disconnected from the vehicle to properly perform the calibration procedure. If a scan tool is connected before this procedure is completed, then new calibration values will not be stored.

Important:  Failure to wait at least 60 seconds will not allow the HVAC control module sufficient time to  clear the old calibration values.

  1. Wait 60 seconds.
  2. Install the fuse.
  3. Start the engine and allow it to run for at least one full minute. Do Not Touch anything.
  4. Turn the ignition off for at least 10 seconds but no more than 30 seconds.
  5. Restart the engine and check the HVAC operation.

Sorry I didn’t get back to you. Taking out the radio fuse doesn’t seem to do anything. There is a 10 amp fuse in the left IP fuse block named “HVAC Control Module, Mode Door Motors/Actuators.” Removing and replacing this fuse will cause the actuators to cycle when the key is turned on. I did try them both as per instructions plus without the car running which is the way I have done it in the past. Neither one worked. I can hear the actuators working. Mine is different than my research I find. Almost all the ones I read about the HVAC is stuck on defrost high heat. Mine is stuck on defrost but will change between hot and cold. It just won’t change to different output vents. I suppose it could be the dash control too. Again, it has been working flawless for years. All I did was change battery’s. Any other thoughts?
Sparky

There are several possibilities. My first thought would be a faulty mode actuator. Secondly the software may need to be updated to overcome an overt ravel condition. You really need a scan tool to see which software version is currently used. A way to overcome that is to try and stall the actuator before it reaches the full defrost position using a tool in the slot of the mode door actuator shaft. Care needs to be taken so as to not get fingers pinched. You can also look at the position of the slot in the actuator shaft to see if it has gone past the molded hash mark.

Sorry to take so long getting back to you. You original question was quite old and took me a little while to see it.

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