A/C Blender Door Actuator

[1sharpguy]

I recently purchased a 2004 GMC Yukon. One morning the battery went dead. I jump started it with my Trailblazer. Then drove to NAPA, purchased and installed a new Group 78 battery (690 CCA). After installing the battery, I noticed that the driver's side A/C will now only blow hot air even though the passenger side blows cold. Reading other forum's, I learned that this is a blender door actuator problem and is common in GMC SUVs and trucks from this era. There is a Tech Bulletin describing the issue. I have tried to recalibrate the actuator using the method proposed by the bulletin..."For auto systems, press the auto button, with the key on. Turn the ignition off. Remove the HVAC/ECAS , 10 amp fuse in the underhood fuse box* or disconnect the battery for one minute. Install the HVAC fuse or reconnect the battery. Start the engine. On systems with auto a/c controls the controls will default to 74 degrees F when the ignition is turned back on. DO NOT TOUCH the a/c controls. Let the engine run for 1-2 minutes. Turn the ignition off for at least 10 seconds but no more than 30 seconds. Restart the engine and then test the a/c controls." I have tried this three or four different times with no success. Also, the temperature guage on the instrument panel does not work (not sure if this has always been the case). The needle lies all the way over to the right past 260 degree and does not move or return.

In another forum, someone suggested that car computers can experience "logic lock" and to fix, it is necessary to discharge the current from all the modules to clear it out. This can be done by disconnecting both battery terminals and holding the two cables ends together for about one minute. I have not done this.

Does anyone have any ideas what I can do? Any problem with the above recommendation to "clear the modules"?

 

[Don Wright]

I know this is a old post but was wondering if you ever got it fixed? Its really hard to diagnose those problems without a scan tool. With a scan tool you can do a re-calibration but you also have bi-directional controls where you can move the blend door back and forth with the scanner. Also you have data pids that give you the position of all the actuators. What else makes it tough to diagnose is you have no access to any of the components without a lot of work involved just to access. I have replaced a lot of actuators and HAVC control heads on G.M cars and trucks over the years.