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. Hey Sparky. I had exactly the same problem as was stated in the repair of A/C coming out of defrost and floor vents and not coming out of the dash vents. I replaced that mode actuator and performed the repair as you layed it out. I turned on the vehicle and it worked like a charm. Cut off the vehicle, got a shower, went back out to go for a ride, and the air didn’t work hardl at all. It would come out of vents that didn’t match up to the mode on the control panel. I took it to the GM dealer and they said they can’t get the air to blow at all now. I had it blowing sporactically yesterday. They said they have to replace the blower motor and resistor at the very least. He said the tech says there is nothing wrong with the calibration. It will cost me $488. I am at a loss! Any suggestions? The vehicle is an ’04 GMC Envoy XUV with Auto Climate control.
    Thanks and God Bless you for all the help you provide people.

  2. I have to thank you for this very insightful how-to, my 2004 Trailblazer thanks you! Took me and my buddy a whopping 4 hours to fix it because in the end we ended up tearing out the entire dash to allow space from above to put the screws in. I have the electronic pedals with the “u” shaped vent piece over them (impossible to remove).

  4. I have almost the same problem but not quite. the left vent only will quit blowing cold air and blows HOT air, will almost burn you it is so hot. Any ideas?

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