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.
hi sparky i johnny, will you tell me how to replace the actuator on my 03 tahoe no ac front vents just defrost thats it, thank you for you help.
Had the battery been disconnected recently before the problem ocurred? Do you have auto or manual a/c controls? You stated that “It now constantly blows air from the front vents and never turns off”. Does this mean that the blower will not turn off at all, even with the key off? Please email me a sparkysanswers@gmail.com
Hi Sparky, thanks for the info. I am having same problem with a 2003 trailblazer, only air from defrost and floor. I bought the new actuator and took it to my mechanic to install it. It now constantly blows air from the front vents and never turns off, defrost works normally, and no flow from floor vents at all.
The mechanic might have moved the actuator before installing it but he claims there is only one way the actuator goes in so he could not have misaligned it. He did a calibration using some computer system he has, but still no luck.
Any ideas?
Thank you!
Typically if the mode actuator is failing or needs recalibration, there will be air flow from the defroster and the floor. No air flow from the panel vents. You state that you have no air flow from any front vent. Can you hear the blower motor turning?
Hi Sparky,
I have a 2003 GMC Envoy SLT 2wd 4.2L
I just recently started having some the problems that are discussed above. I have no air flow from any of the front vents (floor, dash, defrost). The rear ac blows fine.
I tried the recal and after I restarted I had air flow from the floor. I turned ignition off and waited a minute the turned back on. After I turned it back on I had no air flow again.
Could it still be the actuator if there is no air flow through any of the front vents? Thanks in advance!