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.
my 2007 trailblazer will only blow air from the fan and will not adjust higher while driving. When I am sitting idle there is no air blowing in from the vents. What should I check first???
Thanks Sparky Had to install it twice but works great now.
If you can see the white gear lever moving there is something else wrong. Possibly a broken door. I have included a link to a similar vehicle with the same blower system. You will need to copy and paste the address or go to the archives and look for a repair post done in Feb of 2010. About a 2006 Chevrolet Trailblazer with blower problems.
http://www.sparkys-answers.com/2010/02/2006-chevrolet-trailblazer-blower-inop.html
I have a 2004 Envoy XUV and the air blows out the top and bottom only. I took everything apart and could see the actuator turning. Should it be replace if it’s turning, but no air blows through the front vents? On another note, the fan motor works intermittently on speed 5 and always on the other setting. Any thought on that issue as well?
Thanks,
Ken
If the calibration process is interrupted before it is complete the system will freeze. Try recalibrating again. make sure that you do not touch the a/c controls at all until after it is completed and you have restarted the engine. If that does not work you may not have the actuator properly indexed. Let me know what you find or if you need more help.