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.
Hi Sparky! Thanks for all of your help…
I just replaced the actuator and performed the recalibration. Now for some reason the air blows out of the front vents all of the time. I switch the mode to feet and defrost and it still blows out of the front vents.
Any ideas or suggestions?
Thamks again!
The dash does not have to come out. The actuator is accessible by removing the lower dash covers as shown in the post. The only thing that could be slightly different is if your truck has adjustable pedals. If it has adjustable pedals the gas pedal needs to be removed.
I have a 2003 GMC Envoy SLT 4wd with the same problem, air only comes out through defrosters and bottom vents. I have read & seen your directions but wanted to know if we have to take apart all of the vehicle’s dashboard?
What was the original reason for taking the actuator out? Was it already stuck? Has the battery been disconnected recently?
I have 2006 buick rainier i took out my front vent actuator to see if it was sticking i dont beleive it was then i put it back in and recalibrated while recalibrating it move one way and stoped i still have no air coming out of my vents Should i replace actuator Thanks Dave