This 2003 GMC Envoy came in with the complaint that the a/c will only blow out the defrost and floor. Not through the dash vents. I checked codes and found a code B0263 for a fault with the mode actuator. I first ran into this problem after changing a battery in one of these vehicles last year. Whenever the battery is disconnected the HVAC unit will perform a recalibration of all doors. This causes the door motors to be moved full cycle and the mode door will stick some times. I now hook a jump box to the system before changing the battery in Trailblazers or Envoys to prevent a recalibration from occurring. This way I will not be blamed for a stuck actuator motor.
Anyways to change the actuator motor, first drop the hush panel under the driver’s side of the dash. There are some parts that have to be disconnected from the panel including the turn signal flasher assembly shown in the next picture.
Next, I removed the lower dash knee panel to have a little more room to work.
I had to pull a push pin retainer out at the left side of the duct work in order to remove the driver’s floor vent.
Now, I could finally see the actuator on the side of the heater a/c box.
I removed the actuator and installed the new one. Performed a recalibration with my Tech 2 and put all the panels back in place. A recalibration can be done by disconnecting the battery for at least one minute, reconnect the battery, start the engine and leave the a/c controls alone. I would recommend letting the engine run for at least two minutes, turn the ignition off for at least ten seconds but no more than thirty seconds and then restart the engine so that confirmation of the repair can be done.
I do not recommend connecting the wiring to the actuator until it is installed. They come prepositioned for easier installation.
The notch at the lower edge of the gear is an alignment point. There is a corresponding tab on the door linkage that needs to be lined up with this notch.
To purchase the mode valve actuator, please click here. To see updated information about actuator positions and alignment, please click here.
2004 Silverado, 2500HD DURAMAX. Had the a/c vent only on defrost and floor after replacing batteries. Miraculously, after starting and shutting down a few times, it reverted to normal operation. So don’t be in a rush to replace the actuator! It may clear itself.
Brian feel free to email me at any time the address is
info@the-electric-connection.com
There is a link directly above the comment box you were using to post your comment.
Yes my pedals are adjustable. One other thing, there was this really big wire harness running along the bottom of the dash from side to side. That made it so hard to get my hand and a socket up to the module. I did eventually get it after several attempts, followed by some really colorful language. In the end it fixed the problem, and I thank you. Where can we post new topics or questions? There are a few other problems I have had with my ’04 Trailblazer that I have seen similar postings online with no solutions.
Thanks again.
GMoe recently commented that he had an problem with a “u” shaped piece of duct work as well. His vehicle had adjustable pedals and I was wondering, if your vehicle does as well? I have not had the chance to work on one of these and if someone has some pictures, I would be happy to add them, to this post.
hey sparky, I just changed mine on my ’04 TB. I was wondering how you got so much room to work in your pics. I had a ‘u’ shaped piece of duct that goes over the gas pedal. Aside from removing the pedal I couldn’t figure out how to move it, so I didn’t. The hardest part was putting the 2 screws back in. Time to reconect the battery & start ‘er up!!