Vent

[Jbui1980]

After changing the battery on my GMC Yukon XL the ac blows in the lower vents while very weak in the middle vents, any ideas

[txab]

Try this:

 

 

 

You might try the HVAC recalibration procedure:



Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
Re-install the HVAC/ECAS fuse
Turn key on, but do not start. Make no adjustments to HVAC controls at this time
Wait 40 seconds for the HVAC control module and actuators to re-calibrate.

I've always had the best luck at this point by turning key off. Removing key and closing the door. (Signals the BCM of a completed driving cycle)

Then climb in in, start and drive.

You can also disconnect the battery in place of fuse removal

 

 

http://www.gm-trucks.com/forums/topic/150420-air-door-stuck-on-hot/

[Jsdirt]

Sounds like it got a case of logic lock (or more appropriately, ILLOGIC lock ...).

 

Powering down the module via txab's instructions should do the trick.