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 have an 03 GMC Envoy with a similar problem. None of my HVAC controls work anymore. The problem first started when only the 3 and 4 settings worked, but now neither heat nor a/c will turn on at any level or from any of the vents. I already checked the fuses suspecting that was the problem but they are all fine.
Hey Sparky,
I have a 2004 Trailblazer. My problems started while trying to run the AC. It would only work with the blower on number 5. Then it stopped blowing all together and I would smell a slight burning scent. Now nothing blows out at all, there is no burning smell, no matter if it is on heat or AC. Nothing happens at all.
Sparky, just so you know i dont have control over passenger side vents or temperatures either. Im going to try and take it to the dealership sometime next week. Ill just bundle up untill then. now does the passengerside also have these actuators along with the drivers side, or is it just driverside that controls both? Im starting to think it may be the climate control module?
Thanks, Joe.
Hi Anonymous with a 2003 Envoy,
I would suspect a problem with the rear blend/temperature door actuator. It is a fairly common failure point, although I am not sure I have heard your exact complaint before.
If you have control over the passenger side vents, I would say there is a high probability that you need to replace the mode and driver’s temperature actuators. Is there any chance you or someone you know has a scan tool that can “talk to” that HVAC system?