2003 GMC Envoy, No A/C Vent Control, B0263

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.

243 discussions on “2003 GMC Envoy, No A/C Vent Control, B0263”

  1. Hi Sparky.. I have a 2004 Trailblazer with the actuator problem, I got the Part, Installed it, did the recalibration, but now when I change to defrost, I heard two loud bangs, changed it back to blowing out the front vents, again two long bangs, changed it back to defrost with no Bang noise then back to front vents and heard one bang.. What could this noise be? Thanks for any help on this Issue MJ

  4. Sparky, THANK YOU!! These instructions were spot-on. My ’03 Trailblazer’s A/C now blows from the right vents just in time for another Houston summer.

    I ran into two issues that other dummies like me might want to be aware of: there is an actuator right next to the mode valve actuator that *doesn’t* have the plastic gear attached. I’m an idiot, and took that one off first.

    Second: in the ’03 Trailblazer, the mode valve actuator is damn near inaccessible (especially for a big person with long arms). If you don’t have a short handle ratcheting hex driver, get one. I removed everything removable, but I couldn’t even position the actuator by sight–had to do it by feel. Luckily that peg is tall enough that you can feel it line up into the notch–and from there, the actuator’s screw holes were nicely lined up. If you have a mechanically-inclined small child at your disposal, make them do this. 😉

  5. Sparky, and Mike, I went through the steps again and the heat and cold air adjustment started working again on the main vent, but the defrost and floor was not. I did as mike said on the fuse #39 under the back seat and then the defrost and the floor vent now work also! I would like to thank both of y’all with the help y’all provided me on this problem. Sorry it has took so long to report back with y’all. Weathers been bad outside, been hard to get done!

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