Automotive Air Conditioning Information Forum

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"?

I'd like to comment. Mrs. Cusser has had a 2005 GMC Yukon since 2010, and maybe 2 years ago the driver side AC would just turn on to hot while driving; one had to stop and turn off the engine and re-start to restore it to AC. I took off the bottom cover on passenger side, 3 screws (of course the driver-most one was difficult to access because of the floor hump), turned on the AC to get the actuator in the wanted position, then disconnected the wire harness, because in Arizona we needed AC way more than heat (she used the seat-heat function anyway). I left that $^&*&$$&(%#%&* cover off.

So a year ago I go to replace the actuator, wrote down the GM part number and bought its equivalent from Dorman online (maybe half the price of genuine GM part). Actuator is held in place by 2 screws; turns out that once again the floor hump prevents access. I took a 1/4-inch drive 5.5mm socket and ground that shorter on both ends so I could access that $^&*&$$&(%#%&* hex head screw with a 1/4-inch drive ratchet, not easy. So I replaced the actuator, connected the battery and waited, then turned on ignition and waited, and it has worked fine. Oh yes - I left that $^&*&$$&(%#%&* cover off.

On our 1994 Suburban, same had happened, but with clicking under the dash; the mechanic replaced it on that, was over $300, why I did the 2nd one myself. He also said access is ridiculous.

I'll also say that there was trouble with 2 of the gauges, and mechanic removed the instrument cluster and sent it out for local repair (1 day), and it has worked fine since.

So looks like these may be unrelated issues, just GM weak spots.

I have had both issues...blender actuator door malfunction and instrument cluster gauges malfunction. Guages seemed to correct themselves after disconnecting battery and discharging current (holding + and - electodes together for one minute). Blender door still malfunction. Will go by GM dealer today to have codes read. If shows actuator malfuction code, will just buy new actuator off eBay ($30) and install myself. Am aware of the difficulty removing and replacing the cover. Thanks for your info and confirming the same issues.

I'm not aware of us experiencing a code when our actuator went bad; maybe it was a saved code not triggering the "check engine light" for us.