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.
It can have the same code but the part and procedure are different. I am enclosing link addresses to vehicles similar to yours. You will need to copy and paste the addresses.
http://www.sparkys-answers.com/2011/02/2003-chevrolet-silverado-changing-mode.html
http://www.sparkys-answers.com/2011/08/2005-gmc-sierra-air-blows-only-from.html
Is this the same code and instructions for a 2002 Tahoe? Thanks.
Spark,
I have an 05 Silverado Z71 with manual dual climate controls and the full center console. When i start up, air blows through the dash vents. Then after about 30 seconds to a minute, it goes to the defrost and cannot be changed. Do I have the same issue as your original post?
Zach,
Sparky, thank you! The beginning of the vacuum line for the A/C system which pulls off the intake manifold had been snapped, even suspiciously cut! Perhaps meineke looking for some more $$$ out of me. Anyway, popped down to O’Reily’s and picked up a vacuum coupler and the problem is fixed!
Your Malibu uses vacuum actuators for mode control. I would start by looking for vacuum lines that may have been disconnected during the radio install.