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.
Try disconnecting the battery again for at least one minute. Reconnect the battery and start the engine. DO NOT TOUCH the a/c controls and allow the engine to run for 3-4 minutes. Switch the ignition off for at least 10 seconds. Restart the engine and check the vent function. If it is now okay, it will indicate that the last time the battery was disconnected the a/c controls were adjusted during the recalibration procedure. If it still does not work you will need a new actuator. If you need to purchase a new actuator I have enclosed a link. You may need to copy and paste the address.
http://store.the-electric-connection.com/15-73952-mode-valve-actuator-sierra-silverado-suburban-tahoe-yukon-escalade-avalanche-p581.aspx
hey sparky i johnny i have 03 tahoe i just replace battery 2 weeks ago and my front vents its not blowing nothing just the floor and defrost vents can you please tell me whats going on sir.???
Update: I aligned the white notch on the actuator with the notch on the gear in the car, re-calibrated and it works great! Thanks for the writeup. I also changed the blower resistor, so 1,2, and 3 fan speeds work again too!
Thank you for the fast reply. I will give this another shot when I change out the resistor for the blower motor.
It will not calibrate correctly if it is not mounted. The system is adjusting to where the door physically stops moving.