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.
is there any thing else I can do to prevent the recal? Maybe diconnect the actuator or place the selector knob in a certian position??
Using a jump box or battery charger is is changing one battery for another and will not accomplish your goal. I am not sure what is the best way for you to proceed. Try following the large red battery output lead from the back of the alternator up to the battery area. Does it go under the fuse box cover? Does it bolt to the main battery cable? If it can be loosened and removed without taking any other cables loose, I would proceed with, carefully removing it from its termination point. Leaving the rest of the vehicle wiring intact. Having to possibly repair the mode door actuator is much less costly than shorting out the alternator wiring, along with any other damage to varying systems that could result!
I need to remove my alternator to change the thermostat and CTS on my 2003 I6 Envoy. I don’t have a jump box but do have a battery charger. If careful, can I use that to make sure the a/c controls don’t recal? Thanks
Yes, it does. Same part number and the procedure should be about the same.
Sparky, I looked through all of the posts. My vents are doing the same thing….. just the floor and defroster.
I did disconnect the battery to install a stereo. I believe this may have been my mistake.
Does the actuator apply for an 07 trailblazer?
Thanks