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.
one last question. I only have a 10 amp A/C fuse under the hood. is that the correct one? I also have a 30amp HVAC under the back seat. Do i need to pull that one as well or is that something different?
You are correct. For your year model though step 4 can be reduced to one minute.
Hi Sparky, I have a similar issue on my 06 trailblazer LS. had to disconnect battery for a repair and now do not have any air movement through the dash vents. all others work. I have manual temp controls and am going to try your recal procedure and see if that helps. since the length of the post about this I am guessing this is a very common issue. Just to be clear–
step 1 disconect battery or pull fuse
step 2 wait a minute or so
step 3 replace fuse or rehook battery
step 4 start car and let run for 4 minutes (DO NOT Touch controls)
step 5 shut car off for 10 sconds or so (Not over 30)
Step 6 start car again and check if working
step 7 if not working change mode accuater
does this sound about right?
I would suspect the white gear is improperly aligned and the recalibration could not be completed. Check to make sure the black peg on the door gear aligns with the corresponding slot in the white gear.
Sparky, I have a 06 TB and had a no air from dash vents, replaced the actuator and now I always have air out of dash vents, depending on where control is set as to how much. But here is a new problem when you move the heat controls to cold the air flow out of the dash vents gets much more flow even thought I have it in another mode.
It has a manuel A/C control and I have tried the recalibrate.