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.
I should mention, this problem started occurring after I had disconnected and reconnected my battery to work on my audio system.
Sparky,
I am having a similar issue with my 2000 Malibu. The A/C blows cold and hot but no matter where I put my mode knob (top, top/bottom, bottom, defrost) I only get air out of the floor and defroster. I see a lot of posts elsewhere about a blend door actuator but my air changes from hot to cold just fine.
I found a part that looks the same as the one you used, on the passenger side, behind my glove box. I tried moving it by hand but could not. Is this my door mode actuator? If not, do you know where it would be?
Thank you!
Had a problem with actuator controlling air blowing from the dash,too. One of my kids sat in the Trailblazer during his lunch hour with radio on (and daytime lights as well, tho he didn’t know it) and killed the battery. He had someone “jump” the battery to get it going and actuator freed itself and now works fine. Thanks Chris for killing the battery and saving me the time and expense of replacing the blower motor vent actuator!
The mode actuator will be the only one with a white gear arm attached to it. I am assuming that when you and your Dad recalibrated it you actually took it apart and reindexed it. If so then a new actuator should take care of the issue.
I have a 2006 Trailblazer EXT LS and I wanted to ask a question about The Actuator, I had this problem before and my father and I re-calibrated the actuator that was out of of alinement which was on the drivers side and I ASSUME it is the MODE ACTUATOR right? because the air wasn’t coming out of the front vents it was only coming out of the defrost vents. Now my question is, if I replace the bad actuator with a new one will this cure my problem?